Best Tankless Water Heaters 2019 | 20+ Reviews

The benchmarks of Best Tankless Water Heater lies on its capacity (GPM), dimension, efficiency factor, warranty, and many other things. Tankless water heaters can be either gas-fired or take electricity as a source of power. Generally, gas-fired Tankless Water Heaters perform better and heat water faster than electric water Heaters.

Best water heater have higher warranty periods and excellent after-sales services. You do not want to stick with a company who never respond to your query or complaints. Added features like a built-in re-circulation pump, flow control valve, microprocessor technology take a Tankless water heater to another level. Such devices pay a long way to eliminate the wait for hot water at the beginning and balancing the flow rate with different temperature.

So let us have a look inside some market leading on-demand water heater review and dig into their features.

20 Best Tankless Water Heater Reviews 2019 - Comparison Chart


Tankless ​ ​


Fuel Type

Power/Flow Rate

Check ​ Price



27 KW

Stiebel Eltron


24 kW


Liquid Propane

6.6 GPM

Eccotemp Systems

Liquid Propane

1.4 GPM

Stiebel Eltron


28.8 kW


Natural Gas

7.5 GPM


Natural Gas

6.6 GPM

Rheem RTE









18 KW





Natural Gas

6.4 GPM


Natural Gas

8.4 GPM

Rheem RTE 9




Rheem EcoSense
On Demand

Rheem EcoSense




Natural Gas

10 GPM


Natural Gas

9.4 GPM


Natural Gas

9.5 GPM



3.3 GPM

Power Gas 10L


Natural Gas

3.1 GPM

Rheem RTEX-13 240V Heating Chamber Residential Tankless Water Heater



1.5 GPM

Our Recommended Tankless Water Heater Models

The Tankless water heater is the on-demand type water heater. They operate without a tank. So you can get on-demand hot water for all your needs. Two kinds of Tankless water heater are available in the market. They can be electric or gas. The main difference between them is the fuel they use to provide you with instant hot water. There are a plethora of reasons to start using a Tankless water heater. These heaters are energy efficient and cheap.

Eccotemp L5

More than 40 million people go on camping every year in USA. I wonder how many of them fancied the idea of a hot shower while camping! If you are one of them or if you have a RV or swimming pool and felt the need of a water heater for that unit than Eccotemp L5 Portable Tankless Water Heater is your catch.

It weighs only 13 pound so very easy to carry wherever you need it. It has an easy installation process; you only need to attach it to a garden hose nozzle and propane tank for functioning. It has a relative low flow rate of 0.5 gallon per minute to 1.4 GPM. As the flow rate is too low an anti scalding device can be incorporated to it.

It has a 20 minute shut off period to avoid accidents. A 2 D Cell Battery Ignition makes it easy to use at off grid area. One turn off feature is a one year limited warranty period. However a regular maintenance and a little cautiousness can let you forget about this worry for a longer time. That is why despite the low warranty period and a relatively low flow rate, 1064 satisfied Customers has ranked it 4.2 out of 5. And to do all these, you’ll need the instant water heater with shower head. This tankless water heater prices are not too high as its usefulness.

Takagi T-KJr2-IN-LP Indoor Tank less Water Heater

When you are deciding the size that is right for your home, you generally find it by adding up the flow rates of the appliances where hot water will be used. This is why most of the time a higher GPM is preferred. Takagi T-KJr2-IN-NG Indoor Tankless Water Heater is one of highest GPM provider in the market which is the well known water heater for large homes. It gives you 6.6 GPM35°F temperature rise and 3.3 GPM at 70°F rise.

This Japanese on demand water heater gas is also renowned for their longer track records. They give 10 year limited warranty. T-KJr2-IN-LP Indoor on demand hot water heater propane can support homes up to 7500 feet altitude. It is a gas fired water heater which guarantees a saving of gas bill up to 1/3rd if you choose to use it in less than or equal to 131 degree temperature (pretty hot right!). Takagi is one of the best water heater brand in the world.

For comfort of using and living it comes with remote control. Tankless heaters are mostly popular for their small sizes and with a dimension of 6.7 x 13.8 x 20.3 Takagi T-KJr2-IN-NG Indoor Tankless Water Heater is one of the smallest within this capacity. It requires gas inputs of 140,000 BTU. So for a home with 4-5 people and 2-3 fixtures to run at a time this model is ideal.

Eccotemp i12-NG Indoor tank less heater

I do not know about others but I am an energy conscious person that is why I like the fact that Eccotemp i12-NG Indoor tank uses only 2 watts when idol and 1.07 amps during operation.

With a horizontal vent kit system this unit is very easy to install. It also has a sleek black acrylic glass casing along with a digital display and touch screen. It looks no bigger than a big Ipad. It is particularly useful if your home has medium need of hot water. With two bathrooms and dishwasher, washing machine you can choose this model.

Some complain about the vent pipe that comes with the system but an easy solution is to invest a few dollars for a stainless vent pipe this will be so cheap in compare to the total investment for the heater not worthy of considering it as a drawback.

This model has an automatic heat control mechanism and a child lock system. It is Very safe for home with children and elderly people. The outer shell never gets heated up and automatic heating system reduces the need of a minimum flow rate to activate the burner. It is good for homes with 120-volt electric setting so you do not need any additional settings for installation. It flows at a varying rate of Hot water range: 0.6 - 4.8 GPM as with different temperature rises.

Eccotemp L10 Portable Outdoor Tank less Water Heater

We are nature’s fan but technology’s friend. In one hand we want to explore and bewailed with the nature’s beauty on the other hand we do not mind to take a look at what is happening in the city by being updated by Facebook. This is why smart manufacturer has invented technology like portable water heaters. Now where you will take it -to the campsite, pool side, forest or simply mount it in your garden for a Bar B Que party that is up to you.

Ecco temp L10 Portable Outdoor Tankless Water Heater has battery ignition system to equip you with the freedom of taking it to off grid area. A low PSI requirement has been intend to free the travelers for seeking for a high speed water supply, which may be scant in a rustic ambiance.

The digital temperature control gives a range of 80-120°F heating capacity. If you think it is for a single application as I mentioned it is ideal for campsite, than I would like to add that it is perfect for at least two fixtures to run at a time. Thus it is also usable at outdoor for a permanent purpose. So if you are looking for a medium capacity portables gas fired, Eco friendly tankless water heater Ecco temp L10 Portable Outdoor Tankless Water Heater can be shortlisted.

Rinnai RL94eP ​

Rinnai RL94eP Outdoor Propane Tankless Water Heater

With a 9.4 GPM Rinnai RL94eP Outdoor Propane Tankless Water Heater is sure one of the best propane tankless water heater in the market. It has all 5 star shining in its profile at amazon. It needs 10,300 – 199,000 BTU. It has 83% efficiency rate meaning with 1 unit of gas consumption it produces .83 unit of electricity. It is suitable for a home with 6-8 people and can support 5-6 water appliances at a time. However it’s high capacity and durability has made it perfect for commercial usage too. For commercial purpose you will need to buy a separate regulator though.

With 9.3 x 14 x 23 inches dimension Rinnai RL94eP Outdoor on demand propane water heater is small, space saving and neat to look at. It has certification from Energystar indicating it’s supreme efficiency in capacity and in Eco friendliness.

It has a scale of 98°F - 140°F for residential use, however if yours home is at a very cold place with high demand than you can buy the commercial controller and set the temperature as high as 185°F. A temperature lock option is there to save you from risk of scalding. Did you ever come to look for a product and found it has a flawless rating of 5 star? If not than you can visit the site for this best propane tankless water heater and chances are great that it is what you are looking for.

Rinnai RL94iP

Rinnai RL94iP Propane Tankless Water Heater

Another high capacity, capable of supplying very hot water, heater is Rinnai RL94iP tankless water heater propane. It has 9.4 Gallons per Minute capacity. So when 5 people decide to take shower in different bathrooms it does not let each other curse because of fluctuating temperature of water. It is suitable for 5-6 fixtures to run simultaneously and never run out of water. Are you concerned about the rise of temperature? Do not because in residential use it let you enjoy the temperature from of 98°F - 140°F if buy for commercial use with an additional controller you can enjoy up to 185°F.

We have discussed how stainless steel valves are better than plastic valves for durability but the best in the industry is heavy duty forged brass Webstone Isolator service valves which comes with this Japan made water heater.

It comes with a built-in Rinnai Circ-LogicTM. It is a re-circulation program that cycles an external pump at pre-set intervals and temperatures, this feature maximizes efficiency and comfort.

People always concerned about the installation and after installation labor services will be happy to hear that it Rinnai RL94iP Propane Tankless Water Heater comes with 1 Year Labor for Residential Installations. It has a 12-Year Warranty on Heat Exchanges and 5 Year Warranty on Parts. So this is a wise choice for people with high need and best propane tankless water heater.

Takagi T-T-KJr2-OS-LP Outdoor Tankless Water Heater

If you are looking for a non-condensing Propane fired water heater than for a home with 2-3 bathroom, than you can look into Takagi T-T-KJr2-OS-LP Outdoor Tankless Water Heater. With an input of 140,000 BTU this unit can support 2-3 application at a time in warmer climate.

One safety feature of Takagi models are they have an over heat cut off fuse system, that will guard you against the risk of accidents. These small units are often combined with a central heater or with other small heaters so the Japanese manufacturer provides enough provision to link it with 4 units without you to make any visit to home depot or any accessory store. It has all required ports you need.

It is ideal for 2-3 people’s home. It is specially designed for outdoor installation because of the venting requirement. If you are looking for a pilot light option than it will not satisfy you, when on you can hardly detect it as there won’t be any sign unless there is a water flow. Outdoor models have remote controls so that you can control the heat easily from the room if your kid is in the shower or in middle of washing clothes you do not have to go over to the place where the heater is installed in order to control the temperature.

Did I miss anything? oh yes, If you are looking for a very long period of warranty like for 15 year than you would be glad to know Takagi T-T-KJr2-OS-LP Outdoor Tankless Water Heater give 15-year limited warranty on heat exchanger in residential applications and 5-year limited warranty on all parts.

Rinnai RUC98iP

Rinnai RUC98iP Ultra Series Propane Tankless Water Heater

Rinnai the acclaimed manufacturer with Energystar claims they have an ultra modern series of condensing tankless water heater models, Rinnai RUC98iP Ultra Series Propane Tankless Water Heater is one of them. One advantage of it is it has a re-circulation pump. It has effectively used thermal bypass technology to reduce wait time for hot water. It has an integrated pump that encompasses an internal bypass line and thermal bypass valve. Altogether it supplies you with hot water at less time.

It is propone fired and takes 199,000 BTU maximum. With compliance with ultra-low NOx emissions it has achieved Energystar. This is also a Japan made heater so warranty features are also lucrative.

For Residential use it gives a limited 12-year warranty on heat exchanger, 5-year warranty on parts, 1-year warranty on labor. It can also be used for commercial use. With a dimension of only 10 x 18.5 x 26 inches and 82.7 pounds it is very easy to install and matches with your interior seamlessly.

Whatever they say about the wait time and warranty if not good enough for you than the GPM it offers will surely lit your face, that is 9.8.Pretty good and indicates it is suitable for big home at warmer place and medium home for very cold places. It can support 4 showers at a time so if you are in for a high capacity tankless water heater than this is it.

Chronomite SR-20L/240 HTR Tankless Water Heater

You do not come across an electric fixture that has 99% energy efficiency every day, but Chronomite SR-20L/240 HTR 240-Volt 20-Amp SR Series Instant-Flow Low Flow Tank less Water Heater is one of those rare water heater. It offers flow rate of 5 GPM, suitable for 2 showers and a faucet at a time. It was specially designed for under sink hard-wiring.

While installing and selecting the spot for it you should know that it is made for only horizontal installation. Those who want to spend least on installation and have some DYI skill would love hear that it has a rear electric knock out system letting in or out of a wire or cable or pipe through a connector.

If you are not interested to buy a heater that needs a frequent cleaning and maintenance than this heater from Chronomite is bliss. It has a self-cleaning feature. This does not let calcification to buildup and eliminates alkali.

Manufacturer also claim that it needs only 2 seconds to heat the water. These heaters have anti scalding feature reducing risk of accidents and ensuring home safety. Another certification Chronomite SR-20L/240 Tank less Water heater has achieved is that of ADA. So for the lavatory, sink, and dishwasher or for a duel bathroom home this model is a safe and cost efficient choice.

Electric Tankless Water Heater

Every company vows to sale the top rated electric tankless water heaters; however which one is outstanding is a matter of detailed research. I have done some of it and found every manufacturer has something unique to offer. Where Eccotemp has EnergyStar certification and lifelong guarantee, Stiebel Eltron has Advanced Flow Control technology with a smart microprocessor technology that controls flow and temperature to make a balance. Atmor has advanced Thermo Pro self-modulating system that heats up first and reduces electric consumption. Some are the whole house electric tankless water heater like EcoSmart ECO 27, Tempra Plus 29 kW and Rheem RTEX-13. It is tough to say which one is the better electric on demand water heater, let us have a look yourself.

EcoSmart ECO 11

EcoSmart ECO 11 Electric Tankless Water Heater

“Lifetime warranty” is those two magical words that make my eyes wide open. EcoSmart is that one manufacturer who gives life time warranty on faulty parts (conditions applies). But one turn off thing is that it ask you to leave the installation to the professionals in a tongue that ensures if you do it yourself without any certification than you will lose the warranty features. Other than warranty there are many exciting core features of this product, such as it weighs only 6.5 lbs. It needs only 125 amperage and run on 240 voltage supporting line.

If you have a shower with flow rate of 1.5 GPM and a sink with 0.5 GPM than you can easily run both of them together at 67 Degree F. That means it can heat up to 2-Gallon per minute, good for a single bathroom home, or dedicated for a sink or kitchen.

Be sure before buying, that it is the right heater with your electric wiring and voltage requirements. It needs 60 amp double pole breakers for support. Manufacturer terms it as a whole home heater for temperature of 67 degree and above that means it is more suitable for low usage and warmer temperature. If you need water heater for an area warm as 67 degree and have 1-2 people to use it a time than this is a good option. Overall this Electric Tankless Water Heaters model is a great choice.

Ecosmart ECO 18 Electric Tankless Water Heater

South Texas, New Mexico, South Florida, Arizona , South California or any place where temperature is 62 ° F and above are perfect fit for Ecosmart ECO 18 Electric Tankless Water Heater. This is a very compact heater that can easily be wall mounted.

This heater has a dimension of 17" x 14" x 3.75" which means it can save 12 cubic feet of your storage space. Also the self modulating technology let you save 60% of your electric cost. If you want to enjoy the self indulgent luxurious bath of a constant temperature of hot water than Eco smart is ready for it. It has a digital temperature controller from 80°F - 140°F provision of heat in increment at 1 degree interval.

Ecosmart ECO 18 Electric Tankless Water Heater has a cosmetically pleasing outward that can seamlessly fit with your interior. With 2.5 Gallon per minute flow rate, it is water heater for medium category homes. In inlet temperature of 42 ° F -52° F and Ecosmart ECO 18 Electric Tankless Water Heater can support 1 shower and 1 sink simultaneously.

It can perform better at warmer conditions, like if temperature is 57° F-62° F than it can support 2 faucets and a shower meaning while you are taking a bath and someone is using washing machine if another person decides to pour a pot with water or wash hand you will not feel any drop in temperature. This 99% energy efficient instant water heater can give endless hot water supply to 2 shower and 2 sinks at very warm places like 77° F.

Stiebel Eltron Tempra 24 Plus Electric Tankless Whole House Water Heater

If you can put your trust on German technology and engineering than this 90 year old German brand have some high capacity tank less water heaters for you. With 21.5 x 19.5 x 8.8 inches dimension Stiebel Eltron Tempra 24 plus Electric Tank less Water Heater weighs only 15 lbs. The feature I found worthy of highlighting most is that- It has very high Gallon per minute capacity, In 240 volt; with 20 degree rise it can give 8 GPM while at 90 degree rise it gives 1 GPM flow. It also supports a setting of 208 volt.

This is an all electric tankless hot water heater requiring no ventilation. You can easily install it inside home near a place where most hot water consumption is needed. Like many modern tank less heater it has digital scale, It offers a scale of 30°C (86°F) to 60°C (140°F).Ideal for a 2-3 bathroom home with 4-5 people.

One turn off thing for me is its 3 year limited warranty (when installed by licensed personnel), it seems pretty less than some heaters who offer 10-15 years of warranty, in most cases installation, faulty parts assembly and dissembling cost are not covered though. However separate parts of the heaters are attached with screws so though you may not get it covered under warranty the cost and the level of effort given for repairing and uninstalling those parts will not be extensive.

Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater

I find it ambitious when someone say a water heater can save 50% energy cost, Ecosmart is one of them with their Eco smart ECO 36, 36kw 240V Electric Tankless Water Heater they claim to reduce your energy cost up to 50%. You can use it for purposes like washing machine, dish washer, bathroom. It also serves- large Roman-style and Jacuzzi tubs.

With 17 x 19 x 3.8 dimension and 17.4 lb weight it is easy to handle and install. However like all Eco smart water heaters you will risk voiding the lifetime warranty clause if you do not use licensed plumber, electrician for installation. It has a digital scale marking from 80°F - 140°F heat, offering change in temperature at 1 degree interval. Installation of ECO 36 means it will require additional fixtures for supporting it like- four double-pole (240V) 40A circuit breakers , #8 copper wiring; total 12 wires-8 "hot" wires and 4 ground wires.

This is one of the highest capacity water heaters from Ecosmart group. It is made for supporting 4 showers and a sink at a time at a temperature of 37°F. Before you make the decision be sure of your requirements and specifications. If someone says what is the best brand of tankless hot water heater? I would definitely vote for Ecosmart group.

Bosch T 2.5-Gallon Electric Mini-Tank under Sink Water Heater

No this is not a tankless water heater, Bosch T 2.5-Gallon Electric Mini-Tank under Sink Water Heater is still in the reviews of tank less water heaters because of it’s size and easy installation. It comes in 3 sizes 2.5 liter, 4 liter and 7 liter. If you are fond of in line water heater but cannot be in peace with the wait time for hot water after opening the faucet. Than this is the best thing to go for.

It is almost as small as a tank less unit - 13.75 W x 13.75 H x 10.75 Dimension for 2.5 liter, 13.75” W x 13.75” H x 13.5 “D for 4 liter and 17.5” W x 17.5” H x 14.5”D for 7 liter. Weight is 15.5 lbs, 17.4 lbs and 29.5 lbs. It is Smallest in the Tronic 3000 T series and has a capacity to support 3 faucets or shower at a time. It needs 150 PSI minimum to activate and 10 minute to heat up tank full water.

Like the name suggest it can be wall mounted under sink or over the cabinet and be hidden away. A bracket is also included for hanging purpose. You may want to buy a tank less heater for longevity and energy efficiency, these two purpose are also well served with Thick CFC-free foam insulation of Bosch T 2.5-Gallon Electric Mini-Tank under Sink Water Heater.

Eccotemp EM-4.0 Electric 4.0-Gallon Mini Tank

Eccotemp EM-4.0 Electric 4.0-Gallon Mini Tank Water Heater

Well it is not a tankless heater it comes with a mini tank of 4 gallon so that the cold water sandwich problem can be bypassed. It has a digital scale with adjustable temperature control 50 Degree-140 Degree F.

It has Temperature/Pressure relief valve included in the package so there is no fear of water leak or hot water to go back into the cold water tank. Tank feature ensure instant hot water to any fixture and zero waiting period. It has the point of use feature so you do not need to worry about the minimum flow rate to enable the heater.

It is made for residential, commercial as well as for industrial environment. Though it is not tankless it has a space saving feature with 14.5 x 14.5 x 12.9 inches of dimensions. Perhaps 4 gallon tank is not that big after all. It can be wall or floor mounted. If you do not want to display it you can easily hide it inside cabinet with such a manageable size. One thing you need to remember is -it can handle up to 150 psi beyond that you may need a flow valve to reduce your water pressure.

So if you want a water heater that is small yet overcomes the barrier of the wait of hot water at beginning, or if you want an assistant heater with the central water heating system of your home, than these 22.9 pounds weighted 4.0-Gallon Mini Tank Water Heater from Eccotemp is perfect.

Stiebel Eltron DHC-E12 E Electric Tankless Water Heater

If you live in a place with inlet water temperature of 32 degree f and looking for a whole house Electric tankless water heater. Than you can go for it, if you buy this German made tank less unit it can support you with hot water in 2- 4 bathrooms. It comes with a digital scale from 86 Degree F (30 Degree C) and 125 Degree F (52 Degree C)

I talked about the cold weather if you reside in warmer climate like 65 degree or above Stiebel eltron tank less water heater can support 5 faucets with 0.5 GPM and 2 showers if GPM is 1.5. How many people at what condition can use this mostly depends on how often your faucets are busy at the same time and what is your inlet water temperature. Still with the capacity stated you can guess it is suitable for high need home. But it has relatively low flow rate so if you are to use it for many fixtures you are going to need flow rate controller to reduce GPM enough to fit into it.

The product is very small with dimension of only 4.1 x 7.9 x 14.2 inches and extremely light weighted, only 6 pound. I wonder how Germans do that; it weights half than it’s contemporary other branded items. With 240 volt and 12000 watt requirement this unit is good for small homes or for supporting water heater.

A home with 2 bathrooms in a tropical climate where water temperatures are above 65 F can use this tankless unit. This compact water heater can be very easily installed. It comes with a 10 year warranty period on water components and 1 year on electric components. It has a dimension of 12 x 10 x 5 inches and weighs only 7.3 lbs.

You can easily run it for 2 faucets in a temperature above 55 degree F. It has Copper heating elements that help the water to heat very fast, it also protect against galvanic corrosion. It requires 0.5 GPM for activation. It needs a 60 amp fuse and a 6 gag wiring.

However Titan has this distribution channel named Niagara Industries who is responsible for all the repayment solution, no other licensed technician can open the heater as it is sealed. This can be a good thing for those who do not want to take the hurdle of looking for an electrician when a fixture malfunctions. On the other hand if you are not interested to mail it to Niagara Industries and want to have help from your diary of licensed technicians or want to DYI; you may not like this restraint.

Stiebel EltronTempra 29 Plus Electric Tankless Whole House Water Heater

TEMPRA 29 PLUS is another product from Stiebel Eltron under the series of Tempra. The specialty of Tempra series is that it has Advanced Flow Control technology. This Advanced Flow Control technology encompasses a smart microprocessor technology that ensures a steady output temperature; even if flow rates of the faucets vary significantly. Most electric tankless hot water heater do not have this technology and needs a flow control valve extra to be installed to steady or down size the flow of the faucet.

Stiebel Eltron Tempra 29 Plus is a Electric Tankless Water Heater that can run in 240 V or 28.8 kW.It is a compact yet a whole house solution with a weigh of 22.4 pounds. One down side of the product is -this German made tankless heater has a strict policy for warranty, they give Three year limited warranty only when installed by licensed personnel.

Like other tankless water heater it does take a wait when you open the faucet and reach the minimum activation rate of flow. However unlike tank water heaters it will not need another wait period if you have a long term need of hot water or if two faucets are running at a time. It can supply endless hot water for 3-4 showers with 1.5 to 2 GPM. At 90 degree rise it gives 2.5 GPM and at 20 degree rise it can give you 8 GPM flow.

Ecosmart ECO 24 24 KW Electric Tankless Water Heater

Ecosmart ECO 24, 24 KW at 240-Volt Electric Tankless Water Heaters is another advanced creation from Ecosmart group. It has 99.8% energy efficiency like other heaters from this manufacturer. Before buying it you need to look inside the electric requirements of it and if they match with your home’s standards. It needs an Electrical Panel of 200 Amps along with Three 40 Amp Double Poles. With a dimension of 17 x 17 x 3.8 inches and weigh of 11 pounds it is ideal for flaunting or hiding inside a sleek cabinet.

If you are skeptical about China made products you would think twice as this confident manufacture literally offers you a life time warranty (for licensed installation and for electronics, exchanger and element).

This Energy efficient water heater has Energystar certification and a point of use heating system. It works fine with two showers at a time between 120-140 degree or 3 faucet at a time. At colder temperature it can support one faucet and a shower at a time. In my calculation it is enough even if 4 people live in that home because rarely you use two faucets at a time, still if you are not sure than you can check your flow rates and compare other products from the manufacturer.

Ecosmart ECO MINI 2.5 2.5-Gallon Electric Mini Tank Water Heater

ECO MINI 2.5 | 2.5 gallon electric mini tank is an ultimate solution to zero wait time at opening the faucet. Many advanced self modulating technology and microchips of tankless water heater have come a long way to stabilize the flow of water and supply a constant temperature through a prolonged time. Still need of re-circulation pumps have not worn off, one reason behind the fact is tank less water units cannot by pass the wait time at the start.

Only alternative till date is a small tank with the heater. This 2.5 gallon electric mini tank stores up the hot water to eliminate the waiting period. With total dimension of 17 x 17 x 3.8 inches It is such a small tank that you will have a feel of installing a tank less unit.

It is extremely energy efficient like other water heaters of Ecosmart group. It has 5 years limited warranty on leaks and 2 year on parts if installed by licensed professional.

The tank will need 15 minutes recovery time to heat up.I can run on 120 volt and amperage capacity of 12. Cherry on top is it has a Pressure Relief Valve Included. If you have 2 bathroom and other water fixtures like washing machine and dishwasher it can support them at a time at a temperature above 45 degree. From 37 degree and above it can support 2 faucets at a time.

Atmor AT-D24TP-AZ Digital Thermostatic Tankless Electric Instant Water Heater

For Atmor AT-D24TP-AZ Thermo Pro, the manufacture claims that they have an advanced Thermo Pro self-modulating system, this system regulates the amount of energy used to heat the water and it also saves electric consumption. This medium capacity tankless water heater gives 4,6 gallon per minute. So how many applications can operate under this is to be decided by what GPM your shower head or faucets have. In best case it can support 4 applications at Once when 2 Showers have 1.5Gpm/shower head each and two sin faucet with .5 GPM.

Manufacturer gives a specific demonstration on how many faucets can run on different temperature, like in north inlet 37-50 degree f 2 water fixtures can run from 2.45-3 GPM at a time. At Center America inlet temperature with 51 to 60 degree f 1 shower and 2 more faucet can run from3-3.6 GPM. At South inlet 2 shower and maximum one to two faucet can run on 3.6 to 5 GPM.

This China made tank less water heater has a dimension of 17.4 x 5.2 x 13.4 inches and weigh 17 pounds. It has space-saving design is IP54 certification that means it has safe internal components it won’t get wet and needs no venting. It can be a smart choice for your home with a warranty of 7 years against leakage and 2 years on parts.

Stiebel Eltron Tempra 36 Plus Tankless Electric Water Heater

StiebelEltron Tempra 36 Plus electric water heater tankless is another water heater from Tempra series. Water heaters from this series have an advanced Flow Control technology, which encompass a smart microprocessor technology. This smart technology claims to ensure a steady temperature of output even though flow rates of the faucets varies time to time.

It works under some constrains like it cannot work if your water pressure is beyond 150 psi.If you are wondering about what your water pressure is than you should get it tested. Because most instant hot water heater have such restraint of maximum and minimum water pressure, this is why some tankless units do not function at high altitude. You need this piece of information before making the choice to buy any tankless water heater.

The unit need 240.00 voltage and an amperage capacity of 300 A. With 21.5 x 19.5 x 9.5 inches dimensions it weighs 22 pounds and has 3 year warranty under professional installation. So if you have the DYI skill and want to experiment it, I would recommend you to hold the yearning.

It has the capacity to produce 4.5 Gallon of hot water per minutes. With a shower head of 1.5 and a faucet of .5 GPM it can support 2 showers and 2 faucets at a time.

Stiebel Eltron Tempra 20 Plus Electric Tank less Whole House Water Heater

Stiebel EltronTempra 20 plus Electric Tankless Water Heater is a Whole House water heater. Though the company is German, Amazon says this model is made in China. It comes with a 3 year warranty period and the tempra effect. Tempra effect is my version of categorizing these tempra water heaters of Stiebel Eltron which give constant temperature and constant flow despite your inlet temperature and varying water pressure. Manufacture claims they have this advanced Flow Control technology with a micro processor that can balance the flow and maintain the temperature for a very long period.

With 21.2 x 19.4 x 8.5 inches dimension and 16 pound weigh it is a smart alternative to tank water heaters. At 90 degree rise it gives 1.5 GPM on the other hand at 37-40 degree rise F it can give 4.5 GPM. Making it ideal for a small to medium home in cold temperature like that on North America where a1.5 GPM shower and a .5 GPM faucet will be used at a time. Also if you choose to use it at tropical nature you can use 3 showers and a faucet combination.

It needs 0.5 gpm to be activated and working pressure is 150 PSI. It has been tested and certified by WQA against NSF/ANSI 372 for lead free compliance. It seems like a compliant and efficient choice for a small sized home.

Gas Tankless Water Heater

Gas tankless water heater is one with high GPM, low BTU intake, high energy efficiency, easy installation, good ventilation and long warranty. There are many manufacturers who give almost all of them. When going for gas fired tank less water heater be sure to know about the ventilation details, it is very important for your home and environment. A plus point of propane tankless water heater is that-you can take it to the off grid area or install it at a home where electrical wiring do not support your preferable electric tankless water heater. Here are some Exclusive gas water heaters reviews for you to decide which one to pick.

Takagi T-KJr2-IN-NG Indoor Natural Gas Tankless Water Heater

Takagi T-KJr2-IN-NG Indoor Tankless Water Heater is a product of a Japanese manufacturer Takagi. It has a high capacity of 6.6 GPM ensuring 4 applications at a time with moderate inlet temperature. A house with 3 bathrooms and additional fixtures like washing machine and dish washer can choose this instant hot water heater. If you live at a place very high from sea level than you may know that many tankless heaters cannot support high altitude. However Takagi T-KJr2-IN-NG can supply hot water upto 7500 altitude. With a dimension of 6.7 x 13.8 x 20.3 it can save upto 12 cubic feet that would otherwise be lost if installed a tank water heater.

Takagi T-KJr2-IN-NG can supply maximum flow rate of 6.6 GPM at 35°F temperature rise and 3.3 GPM at 70°F rise thus it is good enough for even people at North USA. Takagi has used category III stainless steel in its venting system making it durable and state of art.

This gas fired heater needs gas inputs of 140,000 BTU and complies with ultra-Low NOX regulations. About warranty Takagi is giving a 15 years limited warranty on heat exchanger and 5 years limited warranty on parts, in case of residential use only when installed by a Takagi certified electrician. It is a smart choice for a home of 4-5 people.

Takagi T-H3-DV-N Natural Gas Indoor Tank less Water Heater

Takagi T-H3-DV-N is a Highly Efficient Natural Gas fired condensing Indoor best water heater. Amazon termed it as highly efficient because of it’s high GPM of 10 and 95% efficiency factor. This means in cold weather it can support 3 showerheads and in warmer condition it supports 4 showerheads. Good news for people living at high altitude is that it can run up to 10,100 ft. altitude. It has Energystar certification for high GPM and compliance with Ultra-Low NOx regulations.

It is a 100% natural gas fired heater with gas inputs of 199,000 BTU. Japanese provide all the safety features along with it like-freeze, overheat, surge protection, and troubleshooting diagnostic codes.

It has two heat exchanger the primary heat exchanger utilizes commercial-grade copper alloy. Good thing about copper alloy is that it is 25 times better in transferring heat than stainless steel. Another feature of Takagi T-H3-DV-N is that it can be used for commercial purpose too. It gets 6 year limited warranty for commercial purpose and 15 year limited warranty on residential purpose. It has Maximum flow rate of 10.0 GPM at 35°F temperature rise and 5.4 GPM at 70°F rise so it is perfect for a big home with 6-9 people. If you are looking for a large capacity, environment friendly tankless water heater than this is it.

Rheem RTG-64XLN Outdoor Tankless Natural Gas Water heater

Rheem RTG-64XLN is termed as a “Mid-Efficiency Outdoor best water heater” provides inline water heater. It has 84% efficiency that means when it consume a unit of gas it produce 84% unit of hot water. It needs 120V AC and has to be installed outdoor in wall. It is also suitable for hilly area or a place far above sea level as it supplies hot water to places up to 9,840 ft. elevation above sea level. Though it is to be installed outdoor, you need not to worry a lot about the maintenance and freezing issue as, because manufacturer gives a Freeze protection to up to -30°F.

Rheem is a very modern company and understands your concern of choosing the right sized tankless unit. They offer this EZ- Spec™ Sizing Software – advanced online tool which will play the role of a guide for you to find the right size and model for your home at Rheem.

It heats water after sensing a flow, at 0.40 GPM minimum flow rate it activates the burner. It is a medium capacity water heater which supplies 6.4 GPM at 35° F rise and 5.6 GPM at 45° F rise allowing 2 showers and a faucet to run at a time. If you need a whole house tankless water heater for 4-6 people this can work, no matter what the inlet temperature is.

Takagi T-KJr2-OS-NG Outdoor Tankless Water Heater

Have you ever used original Takagi T- OS-NG Outdoor Tankless Water Heater? This was a popular version but manufacturer Takagi believed in making it perfect by taking some feedbacks so a little change in location of inlets and outlets result is new Takagi T-KJr2-OS-NG Outdoor Tankless Water Heater. The name says that it is only for outdoor installation so install it at a suitable place close to most of the points of use. This will reduce the wait time and won’t let the hot water to get luke warm through the travel. proportional gas valve heats water after sensing a flow of 0.75 GPM.

It comes with a wired remote control well it is not as good as wireless yet when you are at middle of shower or washing clothes this wired remote can be a rakish comfort.

It is 82% Energy efficient and offers a 6.6 GPM. That means 3 shower of 2 GPM and a faucet of 0.5 GMP can run simultaneously. The digital scale has a range of heat between 113-140 degree F so if you are a resident of extremely cold place and have a 2 bathroom house with 4 people and other water fixtures than you can blindly depend on it. This Outdoor Tankless Water Heater is one of the ​top rated tankless water heater in the market.

Rheem RTG-84XLN Outdoor Tankless Natural Gas Water Heater

If you are looking for a high capacity tankless gas hot water heater -Rheem RTG-84XLN 8.4 GPM Low NOx Outdoor Tankless Natural Gas Water Heater is a good choice. The thing that excited me most about this unit is -it gives 8.4 gallon per minute at 35-degree rise and 6.6 gallon per minute at 45A-Degree F rise. Thus a home with 2-3 bathroom and 4-6 people can choose this tough boy.

In case your fixtures have low flow rate and you are not sure about them to function with a gas fired tankless unit than you would be happy to know Rheem RTG-84XLN can work with only 0.26 GPM Minimum Flow Rate. This gas fired heater takes 180,000btus and 20 amp circuit for support.

Rheem RTG-84XLNis complies with Energystar one of industry’s best parameter to evaluate efficiency and capacity. With 14 x 10 x 26 inches dimensions and 54 pound it is not so light weighted like some electrical water heaters but definitely 10 times smaller than tank water heaters.

If you are wondering about the hassle involved in controlling an outdoor tankless water heater then you can shrug the sweat off. Rheem RTG-84XLN comes with an UMC-117 remote control and 10-Feet of thermostat wire for your ease of use.

Camplux 5L Outdoor Portable Propane Gas Tank less Water Heater

Camplux 5L Outdoor 1.32GPM Portable Propane Gas Tankless Water Heater has industry’s lowest activation PSI of 2.So where you take it if that place has a low flow inlet it will not be a barrier for this heater to work. With 1.32GPM it has a relatively low flow rate. Plus side of the low flow rate is it keeps the water hot for longer and down side is, it does not allow more than one fixture to run at a time unless the fixture has a flow rate of .6 GPM.

Manufacturer supplies a 5 feet propane gas pipe with the unit. It serves the purpose of carrying is 34,000 btu/hour. Minimum pressure to operate the propane chamber is 0.4 PSI. Camplux is obviously one of the best rv tankless water heater.

One feature of it is that you need a CSA approval for propane gas supply to run the heating process, for safety reasons (In most cases it is available wherever a gas supply is available). In case you do not have a 12 volt water supply pumps in middle of a campsite, you can still run the unit by 2 D cell batteries. If you are looking for a portable water heater that you can take to tours ,campsites and also use as a permanent solution in your lawn for bathing the pet or throwing a Bar B Que party, than choosing Camplux 5L Outdoor 1.32GPM Portable Propane Gas Tankless Water Heater will be a clever pick.

Rinnai RUR98iN 9.8 Indoor Natural Gas Tankless Water  Heater

Rinnai RL94eN Natural Gas Tankless Water Heater is a high capacity condensing water heater with Gallons per Minute as high as 9.4.It is a very smart choice for those who want to go tank less but is afraid of the weight of hot water in the beginning. It has a Built-in circulation pump. If you are wondering what that is than the information I have from all my research is-it is an integrated system with a thermal bypass technology. This gas tankless hot water heater technology includes an integrated pump, internal bypass line and thermal bypass valve; together they work for less time to heat the water on the flow. It does not need another line for the recirculation pump means less money to spend on installation for extra features.

This unit comes with MC-195T remote controller. The 96% energy efficient water heater consists of dual heat exchangers to provide maximum efficiency. It has a small dimension of12.5 x 10 x 26 inches and weighs 81.6 pounds. I found it a bit heavy in compared to other tankless units perhaps that is attributed to all the built in pumps and valves that gears up it’s efficiency.

It needs 120 volts and 10 A, to operate. If you are worried about the durability than limited 12-year warranty on heat exchanger, 5-year warranty on parts and 1-year warranty on labor is something that can help you to be stress-free. For commercial usage warranty clauses are almost same except for a limited 5-year warranty on heat exchanger. I do not know about you but if I had to buy a water heater for 3 to 4 bath room where occasionally 4 showers and 2 faucets need to work simultaneously than I would go for it.

Camplux 10L Portable Propane Gas Tankless Water Heater

Camplux 10L is another outdoor Portable Propane Gas fired tankless Water Heater. It has 2.64 GPM capacities allowing for a powerful shower and 2 faucets to work simultaneously. It has a Digital Display for temperature control from 46.4℉(8℃) to1 23.8℉ (51℃).It needs gas pressure to be 0.4PSI with maximum power output 68,000btu/hour. It saves 12% of your fuel cost, for example if you fill BBQ propane of 20lb tank you can take 50-60 showers with it. For using it at off grid area it requires alkaline 2D batteries. It works with a very little water pressure of 3.6 PSI and capable to deal up to 110.0 PSI.

Another plus side of Camplux10L water heater is it comes with every spare parts you need for installation, like- adapters, CSA approval gas hose & regulator, gas inlet connector, garden hose, accessories package-included water tape & screws, ON/OFF shower head and pedestal. As it is to be set out door manufacturer incorporated an anti-freezing protection with it.

With Camplux 10L You can go camping or set it by the pool for open air showers, pet showering and forget about safety issues. Because for air safety manufacturer has adapted innovative combustion technology, meaning Oxygen levels throughout the complete burner firing will be lower than 3%. It has a 20 Minuit automatic safety device and a flame failure protection device that guarantees complete safety for home and people around.

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Rinnai RL75iN

Rinnai RL75iN Natural Gas Tank less Water Heater

Rinnai RL75iN Natural Gas Tankless Water Heater is ideal for mobile homes and normal homes. Easy to install and have ENERGY STAR® certification. It is 82% energy efficient meaning with 1 unit input receipt it produce 82% output.

Rinnai is a very safe choice when it comes to the question of dealing with hazards. It has a Temperature lock function so you are guarded against accidental or unauthorized changes to water temperature. With enhanced scale detection technology built in Rinnai RL75iN lessens possibility of serious, long-term damage to unit and you can take prevention beforehand.

About the warrantee period it gives a limited 12-year on heat exchanger, 5-year on parts, 1-year on labor, same for commercial except for a reduced 5 year warranty for heat exchanger. It runs on both natural gas and propane. Minimum 10,300 btu and maximum 180,000 btu input is needed to run it. It is suitable for both residential and commercial usage with a scale of Residential: 98°F - 140°F (37°C - 60°C)and Commercial: 98°F - 160°F (37°C - 71°C).

You need not to know your flow rate before installing this one because it is activated at a very low flow rate of 0.4 gpm (1.5 lpm). At 4.3 GPM it give rise to 70°F at 6.0 gpm it give rise to 50° Temperature. If you are looking for a water heater for a home of 4-6 people, where 2-3 showers can be run at a time than Rinnai RL75iN Natural Gas Tankless Water Heater is a safe choice.

Rinnai RL94eN Natural Gas Tank less Water Heater

Rinnai RL94eN is another high capacity natl gas tankless water heater, comes with maximum 9.4 Gallons per Minute capacity. It has to be installed outdoor for best ventilation. It is ENERGY STAR® Qualified and has 82% EF (Energy efficient factor).So my concern for energy preservation and maximum efficiency is established.

Other than GPM this model is different than the previous model by it’s inbuilt Circ-LogicTM re circulation program. This program cycles an external pump at pre-set intervals and temperatures in order to maximize efficiency and make the wait for hot water zero. It has a scale detection technology that identifies risk of long-term damage and lessens possibility of serious malfunctioning and shut down. SO you can contact an electrician early and not be left with a water heater less home for long.

At 4.7 GPM it gives rise to 70°F at 6.6 GPM it give rise to 50° Temperature, it has a minimum activation rate of .4 GPM, so it is not susceptible to low flow rates. It is also suitable for both residential and commercial usage with a digital scale of Residential: 98°F - 140°F and Commercial: 98°F - 185°F.

If you need water heater for high altitude than this can help as it works Up to 10,200 ft. above sea level. With 9.8 flow rate it can support 4 shower and 2 faucet and at colder place with 6.6 GPM it can support 3 shower of 2GPM and a faucet of 1 .5 GPM. If you live in North with a family of 3-4 members or at a warmer climate with a family of 6-7 people, than this is a great choice.

Rheem RTGH-95XLN is a mid-efficient Natural Gas Outdoor Whole House Condensing Tankless Water Heater. It complies with the low NOx and according to Amazon it has a 95% efficiency factor.

It is suitable for outdoor but inclusion of digital remote control will remove frustration of frequent visits to the heater for temperature control. A 10 ft. long thermostat wire that comes with the package will eliminates the need to buy a longer pipe for installation. Also Freeze protection to -30°F will help you to survive in cold climate without frequent maintenance.

It gives 9.5 GPM at 35° F rise and 7.4 GPM at 45° F rise. 4 showers and 2 faucets can work simultaneously at warmer climate and 2 showers and a faucet can run at a time in a cold Northern weather.

Best thing apart from the 9.5 GPM is Rheem RTGH-95XL’s Hot-start programming technology. This system helps to minimize fluctuation in water temperature during periods of repeated on/off operation. Thus takes care of the “cold water sandwich” problems of the tank less units. It has a Digital display that shows temperatures. This display also shows the maintenance codes and notice alerts to the user by flashing a warning code to call for service check.

If you are looking for a medium to high capacity water heater that can function at high altitude than this might be you take as it works upto 8,400 ft. elevation above sea level.

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Takagi T-D2-OS-NG Outdoor Tank less Water Heater

Takagi D2-OS-NG is an Outdoor Tankless Water Heater that needs 199,000 BTU Natural gas to function. This model was designed for heavier-residential usages such as space heating or domestic recirculation systems. It can also be used for commercial usage like beauty parlors, restaurants. It has a copper alloy for the heat exchanger tubing that protects and enhances the efficiency.

It has a maximum flow rate of 8.0 GPM at 35°F temperature rise and lowest 4.4 GPM at 70°F rise. Thus 4 showers at warmer climate with 2 GPM and 3 showers at colder places with 2 GPM can run at a time without running out of hot water.

​If you already have any other model of Takagi than you can link it with this one and enjoy indulgent lavishness, you can add such 4 units together with existing settings.

It is an outdoor unit with all accessories that can reduce the barriers of using a outdoor water heater. For example it has a remote control for you to use it from indoor, it has built in safety features against- freeze, overheat and surge. Also the digital display for temperature and GPM will occasionally flash troubleshooting diagnostic codes for you to handle the problem yourself or consult an electrician.

Tankless Hot Water Heater Buying Guide

If you want to buy tankless water heaterfor your home use, you should keep in mind some valuable points -

1 ) Tankless water heater flow

water flow

When deciding about which tankless water heater to buy you will receive a lot of information and some key words like flow rate, GPM etc. If you are not aware of this term or need better understanding to make an informed decision than here is a demo guide chart that shows what is usually required as a flow rate and average temperature for different purposes and fixtures. However it can vary based on personal preferences. One thing is to remember that minimum flow rate is also very important and whatever the highest flow rate is, do not buy a Tankless water heater with a flow rate less than your house’s average flow rate.


Average Flow GPM

Average Temp.


4.0 GPM



2.5 – 3.0 GPM


Washing Machine

2.0 GPM



1.5 GPM


Typically tankless water heaters can give 5 GPM at a rise of 70 degree Fahrenheit. This covers a usual home’s need effortlessly. Some tankless water heaters have the feature of thermostatically control. Such tankless water heaters can control output water temperature according to the water flow rate and inlet temperature.

2) Tankless Water Heater Warranties

For a durable fixture like tankless Water heater warranty and clauses of warranty is very important. Mostly manufacturers offer warranty of 

  • Minimum 1 year
  • Maximum life time coverage (conditional)

Other clauses manufacturer attach are-

  • No labor
  • With labor
  • Replacement of faulty parts only
  • Replacement of whole system within a short time if found it was faulty from beginning.
  • Warranty on burner only or heat exchanger
  • In case of replacement with mailing charge or without mailing charge
  • Life time warranty on repairmen of parts.

Conditions typically suffixed are-

  • Warranty void if not installed by a licensed electrician and plumber.
  • Warranty void if codes of plumbing violated.
  • Warranty void if found used for other purposes beyond the scope or a stipulated hour of use.

So what is the best?

In my understanding ‘More the Merrier’ that is more years of warranty is better. It gives a sense of security for longer time and a conviction that the unit is designed for long years without complains. Longer years of warranty also come with strict and expensive conditions like-void in case of not installed by a licensed electrician and plumber. Such clauses simply ask you to spend 300-900 dollar extra. However if you are not an expert or have previous record of DYI skills you better not risk voiding warranty clause and hire an expert.

3) Tankless Water Heater Size

Based on the peak hour demand of your house’s hot water you have to decide the size of the tank less water Heater.

Here is a work sheet Adapted from information from the Federal Energy Management Program Energy Cost Calculator. To find out the real maximum demand of GPM at an hour of day.

Worksheet for Estimating Peak Hour Demand/First Hour Rating


Average gallons of
hot water per usage



Shaving (.05 gallon per


Hand dishwashing or food
prep (2 gallons per minute)


Automatic dishwasher


Clothes washer


This work sheet can help you to decide the flow and Fahrenheit rise combination you are looking for.

In determining the flow rate,

Add up the flow rate of the fixtures you believe will be running same time or use the worksheet above.

In determining the rise of temperature the formula you need to follow is

Desired water temperature – Inlet water temperature.

4) Endless Hot Water

When you go through the tankless water heater reviews you will definitely come in touch with the word ‘endless hot water’. This has become more of a tank less water’s business jargon which stands for the impression than you can run multiple fixtures and need not to worry that hot water will finish. Once you have successfully figured out what is the suitable size of tankless water heater for your home than you can easily enjoy ends less hot water.

For this purpose gas fired tank less water heater are more efficient and less power consuming. In tank water heaters you need to figure out the perfect size too, still you go through the trauma of what if water finishes! It takes time to pour and reheat the whole tank. In tankless water heater you can enjoy hot shower and another 1 or 2 application at a time because the GPH for your tankless water heater and flow rate will balance it out and keep providing hot water as long as you need. Water gets hot immediately through the heat exchanger mechanism so there is neither a tank nor a chance of water of the tank to end.

5) Save Space

Tank water heater has a good feature of supplying instant hot water, but the downside of this feature is many. One of them is the lionize space it eats up.

For Example-

Dimension of tank water heater

Tankless water heater dimension



SIZE (MODEL:ENT 308-6,408-6,508-6)




2 person






4 person




18" x 14" x 3.75"


5-6 person




18" x 17" x3.75"


This table you can see a comparison between two companies (American standard and Eco temp) different models for different sizes of water tank. Tank water heaters are twenty times heavier and five times or bigger in compare to tankless water heater. So the space saving effect is evident from the chart.

6) More Energy Efficient

Tankless water heaters are more energy efficient in 3 ways -

  • It has no stand by loss-

Unlike traditional water heaters tankless water heaters do not run when not in use. In other words it consumes power only when someone opens the faucet and requiring hot water. This causes less power consumption and less cost of electricity. A house with a need of 41 gallon of water every day can enjoy 24%-34% energy efficiency every day. For a home with 86 gallon need of hot water enjoy efficiency up to 51%.

  • Use of copper heat exchanger-

Tank less water heaters generally use copper heat exchanger. Like aluminum, nickel copper also has this excellent corrosion resistance. Use of copper heat exchanger in the heater, improves heat conductivity and reduce corrosion. Result of it is increased energy efficiency.


ENERGY STAR® certified tank less water heaters are estimated to save 100$. ENERGY STAR® has strong requirement of high energy efficiency

Criteria for
Qualified Electric Storage Water Heaters

Criteria for
Qualified Gas Storage Water Heaters

Criteria for
Qualified Gas Instantaneous Water Heaters

EF( Energy Efficiency ) ≥ 2.00 for ≤ 55 gallons

EF ≥ 0.67 for ≤ 55 gallons

EF ≥ 0.90

EF ≥ 2.20 for > 55 gallons

EF ≥ 0.77 for > 55 gallons

GPM ≥ 2.5 over a 77° rise

FHR( First Hour Rating )≥ 50 gallons per hour

FHR ≥ 67 gallons per hour

There are some other criteria like warranty to be higher than 6 years on parts too and safety features. With such criteria this trademark is ensuring more energy efficiency. EF stands for energy efficiency. 87% EF means with 1 unit of power consumption the heater transforms 87% of it into hot water and emission is minimal. Higher efficiency also signifies high environment friendliness.

7) High Quality/Longer Lasting Product

Tankless water heaters are durable from traditional tank water heaters. Tankless water heaters have 20 year or more life expectancy in general. All parts of Tankless water heaters are detachable therefore every faulty part can be detached and changed this increase longevity even more.

8) Increase Home Resale Value

If you are a home owner and have a tankless water heater installed, you would be glad to know-According to Chicago Tribune a home with tankless water heater prices more than a same type home without it. Why? The answer is home users perceive tankless water heater as an added value to a home. More people are buying it every day and proffering it because tankless water heaters are new edition to green home appliance. They emit negligible carbon monoxide (gas fired tankless water heaters only). They saves energy, they save cost of electricity and leave environment detrimental footprint. Today intelligent users prefer a tankless over traditional water heaters. Moreover a home with tankless water heater installed means saving 300-900$ on installation cost along with the price of the water heating unit.

Risks of accidents are minimal with tankless units. Many of them have shut off option in case of any error diagnosed internally. Scalding risk is also close to zero with anti-scalding options, and child lock in many tank less units.

When conscious home owners compare these options they prefer a home that already has an installed tankless water heater for their home.

9) Consider Capacity

Capacity of a tankless water heater is based on following Three (3) things-

  • How many people will be using the hot water in a home?

If your home has 6 people you will need a unit with more capacity and it will cost you more.

  • How distant are the point of use

If your home is big like 2000sft your wash rooms are located in different stairs and heater is at outdoor or at a distant place than it may happen that when you go for a shower hot water coming from a distant place gets luke warm after reaching your faucet. Effective Absolution is placing the water heater at a place nearer to all bathrooms and laundry room or adds two heaters for two floors or east wing and west wing (or any way you can find is suitable to equally divide your home according to your need)

  • How much temperature rises?

This feature determines how powerful the water heater is. Generally 70 degree rise on 5 GPM. Look for a heater that matches your demand.

Also factors like what is the desired flow rate and what is the inlet temperature of your water can greatly impact on capacity of the water heater. High inlet water temperature will require a relatively low capacity tank less unit.

10) Anti-Scald Devices

Anti scald devices are synonymous to automatic mixing valve, compensation valve, tempering valve. Job of such device is to mix both hot and cold water in a way that guarantees person who is using the fixture do not get scaled or burnt due to –too much of hot water flow or too less of cold water flow. Until 2014 anti scalding devices where not much in plumbing industry. Homes did not have any such fixture installed in their main line. But emergence of tankless water heater, low flow rate valves and rising awareness to be protected from domestic accidents has accelerated use of anti scald devices.

If you are wondering why someone will get burnt and need such protection that the typical scenarios are mentioned here-

  • If set water temperature too high
  • Use of tank less water heaters can increase the risk
  • Use low flow rate vale or devices for increasing water use efficiency.

When using a tankless water heater, that heats up water in the faucet a little more use of water from another fixture like-simple toilet flush or starting a dish washer can cause the cold water flow to go down significantly. As a result the imbalance from low flow of cold water and high flow of hot water may cause you to get scald. In such cases you do not have the option to use the hot water faucet manually so control of it goes away, making you prone to serious accidents.

Solutions are three - 

  • Buy a tankless water heater within built anti scald device
  • Install anti scald devices at the fixtures like-shower, faucet where chances of direct heat exist
  • Manually install an anti scald device in the opening of your tank less water heater.

Many manufacturers are offering tankless water heater with anti-scald devices. This added feature is surely adding a bit extra price tag to the product. The decision is however yours whether you would buy the heater with this feature of prefer to install anti scald device manually.

11) Brass vs. Plastic Drain Valves

Drain valves are there to hold on the extra water that try to comes back to the cold water inlet from hot water pressure. Drain valves do not let them go back and hold them inside. Bras and plastic these two types of metal are used to make drain valves. Bras drain valves are durable than plastic ones. Tank less water heater which are hooked outdoor need these drain valves properly cleaned before freezing weather, otherwise they can simply get frozen and break.

12) Glass-Lined tankless water vs Stainless steel tanks

Glass-Lined tankless water heaters gives the benefit of low corrosion. Depending on the ph level of the water of your area mineral and chlorides can store up in your tank less unit’s valves. Glass lined tankless water heater are less prone to chlorides and resist its storage. However there are other options in the market like Stainless steel tank water heaters. Which are more durable less heavy and gives a limited life time warranty. Before choosing between these two you should consult a plumber If your area is good for this type of not.

13) Digital Displays

Most tankless water heaters come with a digital display feature. Some come up with multiple remote. Digital display is a convenient feature that let you know what is going inside the unit.Generally they show the temperature & GPM. Some also show internal error signs or problem warnings. Some are touch sensitive some have switches. It depends on your choice which one you would choose.

What is Tankless Water Heater ?

By definition tankless water heater is a water heater without tank. They are high powered and produce hot water on demand. They use the power supply only during operation therefore power consumption is remarkably low.

The technology of tankless water heater lies in the burner or heat exchanger. When the power switch is on power ignite the burner.

A flow sensor is present in such heaters. It senses the minimum flow upon which it activates the burner.

The burner consists of copper heat exchanger. Heat exchanger’s job is to pass on heat and transform a medium from hot to cold or cold to hot. Generally copper heat exchangers are used for their high thermal conductivity and ease of fabrication and low cost nature.

water heating
ultra interior top

A negative feedback loop also exists that helps to bring water to target temperature. A digital dial is set at the heater cover where user can set the desired temperature.

As water pass through it gets hot. When water heats up it produces pressure upward, when it happens hot water eventually ends up going back to cold water inlet.

A pressure relief valve that is generally installed in a water heater let this pressure go off. Otherwise the hot water pressure goes back to cold water inlet and enters in the municipal tank where the pressure gets relieved. However presence of a pressure relief valve make the job smoother and hot water does not go in to cold water inlet.

A pressure regulator can also function in similar way, it controls the flow and do not let the hot water enter back to cold water tank, this is called closed system. When a closed system exists the tank has to be near it too. If not sometime the pressure valve can leak, but that is another story we will discuss later.

Types of Tankless Water Heaters

It can be 3 type power wise-

  • Gas fired tankless water heater
  • Electricity Fired tankless water heater
  • Dual power-Electricity and battery or Gas and buttery fired

Tankless water heater can be of 3 types based on functionality

condensing non-condensing RUC


Non condensing tankless water heater is the first generation of tank less units that give hot water on demand. They have Efficiency Factor 82%-85%. However the efficiency drops when used for short drops like-hand wash. They are well known in Japan and n Europe for their reliability, but the poor venting system of this type requires users to install additional stainless steel vents, costing some extra money.


Condensing tankless water heaters are the second generation of tank less water heaters. They have two heat exchanger one is same as that of non-condensing and termed as primary heat exchanger. Other one termed as second reuses heat the exhaust to further heat the water.It has higher efficiency of 92-94%. Also venting is inexpensive through PVC but it goes out weight by high unit cost. Like non condensing water heaters it cannot go beyond the lower efficiency for short water draws.

Condensing Hybrid:

The third generations of tankless water heaters are called Condensing hybrid tankless water. They are most fond in USA. Though named as tank less it incorporates small – between 1 liter and 2-gallon tank. This reserve is kept to resolve the inefficiency of high water consumption for short draws. On an average Efficiency factor is 94%, but it can reach up to 96% Efficiency factor. It also addresses the cold water sandwich too. With inexpensive PVC venting system So far these are best, however as it is still fresh in market fewer models and smaller companies with questionable warranty and quality issues.

Why Install a Tankless Water Heater?

Some reasons to install a tankless water heater are many

  1. Space saving- When a tank water heater eats up spaces as large as 12 cubic feet or more. A tank less water heater is not bigger than a laptop some are as small as ipads. So the space solution it provides is hard to ignore. Especially for kitchen and small bathrooms these are more than use full with their sleek and neat looks they are part of interior décor. You can use hot water for washing your major household items like juicers, blenders and utensils.
  2. Portability- Some tankless heaters has the feature of portability; just connect it with a water source and power source and they will bring you hot water in middle of a jungle. Can you imagine that with a tank water heater?!
  3. Energy saving- A tank water heater never really shut off, even when you are in vacation. A tankless water heater on the contrary works only after sensing a required flow of water. Naturally that translates into lot of power saving.
  4. Light weight- Tankless water heater weights 10 times less than traditional water heater. This feature makes it much easier to install. Light weight reduces risk of accident.
  5. High capacity- Tankless water heaters let more than 2 or 3 faucet to have hot water. Depending on capacity number of faucet may increase. One needs not to fear of finishing all water from the tank, because as long as the flow sensor realizes a flow it will supply hot water seamlessly.
  6. Alternative source of energy- Tankless water heater can take electricity or gas as a power with source. So if your home’s electric configuration does not comply with an electric tank water heater or if you live in an off grid area you can choose a gas fired tankless water heater.
  7. Saves water- People far from the point of heater need not to let the faucet open for long to have hot water stored in a distant hot tank. So gallons of water are saved.
  8. Safety- Tankless Water Heaters control water temperature to exact Fahrenheit thus it avoids risk of scalding. Some heaters have auto turn off feature for safety reasons. Some has child lock too. The exposure from dissolved toxic metals is also removed as there is no tank there is no risk of such toxicity from high concentrations in hot water tank.

Where Install Tankless Water Heater?

When installing a tankless water heater where to install it can vastly influence its performance later some things you need to consider before you decide the place-

For whole home water heaters

  • Where the previous heater was has water pipes and gas line installed in that place already. So installing new one at old place is a logical one. Gas lines may need to be changed if new heater is gas fired and has a large BTU transfer rate.
  • If it is a gas fired tankless water heater venting requirements are crucial. Vent has to be at least 3 feet from operable window, when it is vented though wall.
  • If it is vented through roof, a long enough vent has to be installed. So basements are not the suitable place to install the water heater that needs ventilation through roof.

For Point of use water heaters

For point of use water heaters, tank less water heaters are best to be placed in close proximity to where the faucet would use the hot water. Being said it there are some dangerous area where you better not install your electrical appliances like water heater for example-

1. Under the air condition line (water can drip into it)
2. Above or down the electric box (it can catch heat or fire)

  • Know about electric panel and house’s plumbing configuration (that will help future repair issues and water heater’s performance)
  • Know about local building codes. (In every installation manual you will learn a plenty about them and knowing them is vital in making right decision about installation location)

Why are Tankless Hot Water Heaters More Efficient?

Tankless water heaters are the new generation of water heaters. If you open the internet and Google why they are better you will get plenty of article convincing you how they are much better than the tank water heaters, some may be cynical are they really efficient? Or this is simply marketing schemes? Well to know it better you may need to use a tank heater and a tankless heater side by side.

I confess I did not try or experimented like this however I have gone through the reviews of people who did use both. According to them tankless water heaters are more efficient because-

Hot water only as it is needed

Unlike tank water heater who keeps running day long to give you hot water, this type only runs as senses a flow. So power consumption is 15-20% less. Tank less water heaters generate less energy losses associated with storage water heaters, it is as simple as the theory-run less use less power.


ENERGY STAR® is a trademark that guarantees after estimating that a typical family can save $100 or more per year with using an ENERGY STAR qualified tankless water heater.

Low Fahrenheit and pilot light

If you set the heater for a lower heat set up it will also save more energy. Again if your heater incorporates a feature like pilot light it will consume power even when not working. This does trade-off some energy efficiency effect, so you need to decide if you need such feature or not. Even if it has this feature you can still save power by choosing to switch this option off while not in action.


Most tankless heaters have a life expectancy of 20 years. With changing faulty parts they can give more life time however tank water heaters have life of 10-15 years at max.

How to Install Tankless Water Heater Gas?


Generally people install new gas tankless water heater in same place where old water heater was. It is convenient as there water line and probably gas line (if previous one was gas fired) already exist. Then step by step follow these processes as require-Turn off the power than turn off both water and gas supply valves and power. Than you need to first disconnect then drain the old water heater.


Your existing gas line may need to install a tee and valve. To attach your old line of gas with new heater you can use a flexible gas supply line. You need to run a new gas line from the tee to the point where the line can easily catch the new water heater.


Use copper pipe to attach new hot and cold water lines to the existing water lines. This new line will go into water heater. In order to pipe securely in the wall, use hangers. They will hold the pipe against wall. Also this will make it easy for insulation of pipe later. It is recommended to clean the pipes and connectors before soldering. This help to remove oxidation. In order to soldering you need to apply flux to the end of the pipe. Then you need to slip pipe and connectors together. Start soldering by heating the copper with a torch.


Some water heaters are ready to be hung some are better to mount in a platform.If you want to mount the tank less heater in platform, than you can build a platform with 2 x 4-inch pieces of lumber. Through this you can mount the new tank less water heater 4 inches from the wall.


Follow the manufacturer instructions and connect the shutoff valve and sediment trap to the water heater. Now attach the gas supply line with the shutoff valve and connect the water supply line with water heater. It is very important to check for leak this can be done by bleeding the gas line. then turn it off until installation is finished.



Exhaust Adaptor Ring
Intake Cap


Installing the water heater’s vent is also a major part of the whole installation process more or less they are same and a manual with the heater will guide your way through it.


It is time for the last stage of turning on the water heater after taking all the trouble. It is simple you need to insulate the hot water pipe that comes from water heater. Turn on the gas and plug in the water heater. Of course it is aligned with any further special instruction that may come with the manual.

How to Install on demand water heater electric ?

ultra crossover mode new

Find the amp required-

To figure out amp read volt and watt in the label of the unit. Divide watt by volt and you can get the amp.

Stress test-
In case of electric water heater a lot of emphasis is given on the capacity of the breaker. So do the stress test of the main breaker. Generally all amps have highest power up to the 80% capacity that they stand your tank less unit needs a 50-60 amp breaker you will need 60*1.20=72 amp breaker or more whatever is available nearer to that value in market. So do the math and check if your existing breaker is powerful enough or you need a new one.

Check if the unit is heated and the manual

  • If the unit is heated you cannot install the unit.
  • Check for manual instruction.
  • Check in the electrical rating plate that shows voltage and wattage or you can look at product spec sheet. You should Consult Tankless manual if it is available.
  • If manual asks for using a licensed plumber electrician and says your warranty will be void if you do it other way than you should consult a professional and get things done by them.

Check inside for wire connections

Check the manual and the unit to decide how many circuit breakers it may need .A tank less unit can need 1-6 circuit breaker and wires are to be connected in those terminals separately. So look for it and do according to the manual.

Install some additional if required

On demand electric water heater cannot heat up water as fast as gas heaters. Electric gas heaters use much electricity to produce hot water. So in order to reduce energy consumption you can add a tempering tank to preheat incoming cold water. This will keep thermostat setting low, reduce consumption. For recovering from lower water pressure you can add low-flow shower heads.Beware if water moves too slowly through pipe, flow sensor sensitive tank fewer units may not activate.

  • First remove the existing heater.
  • Expose the pipes and mark the spot where to install the new heater.
  • Mount the tank less heater in selected place.
  • Than with the compression fitting that came with the fixture Install the water lines to heater.
  • To remove air from the line you will need to open the main valve and let the water run for 2 minutes.
  • Check the electric codes for appropriate wire gauge and breaker size.
  • After completing connection turn on the breaker and look for the model specific signs of standby mode.
  • Set the temperature to your choice and open the faucet to see if the heater is working.

How much to install a Tankless water heater?

The cost of installing a tankless water heater varies based on many factors like manufacturer, gas-fuelled or electricity driven, Capacity, labor cost, types of equipment & your living region also. The installation cost of an electric Tankless water heater cost from $800 to $1400. Tankless gas heater installation cost from $1800 to $2000. Without installation, the value of the Tankless electric heater is around $800 & the price of the gas-powered heater is about $1400.Now, if you need to repair the wire system of a whole house or if you need a very high capacity tankless water heater then this overall cost will be more. Before going to market, you can set your initial budget based on this post. Since this is a hugely useful machine, your invested money will be a good use for it. Your perfect decision will help you to get the best price tankless water heater.

How Do Tankless Water Heaters Save Money?

Tankless water heater saves money by not running without need. Demand type water heater only run and consumes power at demand of hot water so they save money while idle.

For homes that uses 41 gallons or less of hot water daily, Tank less water heaters can save 24%–34% more energy than conventional storage tank water heaters. If usage is 86 gallons efficiency is 8%–14%. More saving of energy only means saving money.

What Size Tankless Unit Should I Purchase?

I personally believe there is nothing wrong in wanting to save money by a little adjustment however this is definitely not feasible when you are determining the size of the tankless heater for your home. Under sizing your tankless water heater in order to save money will eventually leave you in losing end and, most likely in a cold shower.

Size determination depends on-

  1. Temperature
  2. Flow rate
  3. Fuel or power source

Know your demand (Flow rate GMP)

Determine the number of appliances you plan to run by hot water. Ad up their flow rates, the sum is the flow rate you need from your tank less water heater. If the sum is too high and cannot match any tank less water heater in the market a solution is to install a low flow rate fixtures.

Know your desired Temperature

If you subtract the inlet temperature of your water from the temperature you desire to achieve than you get the temperature rise you are looking your required temperature is 155 degree and your inlet water is 55 degree. So the tank less water heater you are in need has to give a temperature rise of 100 degree.

Type of tankless water heater

Same capacity gas tank less water heater will heat up faster than electric tank less water heater so keep that also into mind when determining the size.



TEMP IS 50 1


Total GPM











Washing Machine










Kitchen Sink







So this house with above fixtures and flow rate needs a tank less water heater with 11.5 GPM at rise of 70 degree in max. This is extremely unlikely that all the fixtures will be used at same time. So you can add up flow rates of maximum number of fixtures that can be used at same time that will also help you to determine the size.

Tankless Water Heater Maintenance

To get long lifespan, you must maintain your Tankless water heater on a regular basis. In every month you have to flush and clean your device at once. During flushing, you have to change filters and drain the system entirely. This extra hassle of maintenance sometimes is not bearable in our busy lives.

How to Clean a Tankless Water Heater?

The cleaning or flushing procedure of a tankless water heater is following:

  1. At first you have to switch off the electric circuit of the heater. If it has a gas heater, then spin the gas cutoff anticlockwise to turn it off.
  2. Then you have to access the wiring of the tankless water heater’s unit with a screwdriver for removing the cover plate. Then use a non-contact electrical tester against the heater wiring towards the terminals. You have to turn off the main circuit breaker until all wires materialize that no power is left to access the system. After that, the cover plate should be replaced.
  3. Water supply valve and the main hot water valve should be turned off.
  4. Now you need 2 garden hose for this step. One end of the 6 foot garden hose should be attached to the vent of the pond pump and the other end should be attached to the cold water isolation valve. The second garden hose will be attached to the hot water isolation valve. The couplers of the hose need to be tightened with an adaptable monkey wrench.
  5. The open end of the second garden hose and the pump should be placed into a large sized bucket. Now five gallons of clean and fresh white vinegar needs to be poured into the bucket.
  6. You have to propagate the vinegar into the heater. Turn on the pump placed in the bucket and then open both the cold and hot isolation valves.
  7. Now you need to allow the pump to propagate for 45 minutes and after that the pump should be turned off. Then the vinegar should be exhausted from the heater through the hoses inside the bucket. Cold water isolation valve has to be closed.
  8. After dumping the vinegar the open ended hose needs to be placed into the bucket. Turning on the valve of cold water supply, allow the water to flow for 5 minutes into bucket. Then disconnect the hoses from the valves after stopping the supply of cold water.
  9. Turning off the hot water isolation valve, the inlet filter screen has to be removed. To clear any deposit inside, the screen needs to be cleansed. Install the screen again.
  10. Following by the cold-water supply valve, the hot water valve has to be turned on. To bleed any air from the hot water lines you have to open a couple of hot water faucets. After making sure there is no air in the lines close the faucets.
  11. Now you have to check thoroughly if there is any leak in the heater’s connection. Then you need to turn on the gas supply valve and check the circuit breaker of the heater. Finally, make sure if there is hot water at the faucets.

How to vent a Tankless water heater?

This is one of the most common concern that how to vent a Tankless water heater. The concern is right because if you fail to vent your tankless heater properly, then your house can suffer from Carbon-monoxide poisoning. The heater also will fail to live up to its full lifespan. It is all about choosing the right venting system as per your house condition. However, to some people, it is very intimidating because of the availability of lots of information on the internet. We will try to help you by detailing some options of venting for the tankless water heater. You need to choose which one is the perfect venting option for you.

Direct Vent system:

By this system, combustion air comes from outside & supplies necessary oxygen to the burner for the combustion process. There are two vent pipes linked from the water heater to the outside area of your hose. One tube is to supply fresh air to the burner & through other pipe exhaust gas is vented outside. This system prevents your house to be damaged from Carbon-Monoxide which can result in accidental fires also. The direct vent can be done in both vertical & horizontal order. This direct vent method is more popular in common environmental areas.

Non-Direct Vent system:

In non-direct venting process, air is pulled to the burner from inside space for continuing combustion process. An electric blower fan is used to draw the air to the outdoors. So there is a risk of carbon monoxide gas poisoning which is a safety issue. Better to check the manufacturer’s manual before choosing this venting system. Venting can be done in both horizontally & vertically.

Outdoor Vent system:

Combustion air is received from the environment around it. It also exhausts in the same way. If your living area is warm enough, then you can choose this system. We recommend you to get a suggestion from your water heater supplier for deciding on venting system. Safety first!

Final Verdict

Water heater consumes 20% of the total energy a house consumes. So price is not the only factor when you are making a choice. Durability, maintenance, efficiency, safety, energy saving feature, size, weight installation cost, and ease, existing infrastructure support all these are very crucial points. May need to spend some extra money to fix the issue like you can choose a heater without flow rate controller than buy a low flow rate fixture later and install.

However, our vision was to let you know some features are not worthy of adding then and some are not even possible to add them. Like if your house has wiring that does not support your specific model of the tankless unit than you have no other option to change the model, because replacing the installation is impossible. Also be very sure to maintain the amp guide do not risk it by using a less powerful breaker or less numb of switch this will shut off the whole system.

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