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Best Tankless Water Heater 2018 – Reviews & Buying Guide

Best Tankless Water Heater 2017 Reviews and Buyers guide

Best Tankless Water Heater is it what you are looking for? Tankless water heaters are also called as “Instant” or “On-Demand” water heaters. Yes, tankless heater produces hot water instantly whenever you require, and they don’t run 24/7 like tank water heaters. Also, tankless heaters are 15 to 25% more efficient, which means you will save more money on your electricity or gas bill every month.

Saving money on the energy bill is one significant benefit of many others, tankless water heaters occupy very less space, unlimited supply of hot water, longer life, low maintenance and eco-friendly.

Selecting the Best Tankless Water Heater for your home is a difficult task as there are a lot of features and factors you need to consider. Most of the people in The United States have very less knowledge about tankless water heater as they are new to the market. So, if you are one of them, then you should definitely read our Best Tankless Water Heater Buying Guide to learn more about them.

If you are well informed about Tankless Water heaters, then you can directly read our best tankless water heater reviews where we have selected them based on features, technology, fuel type, GPM, user ratings, quality and price range. We have reviewed the products suitable for different households like whole house (3+ bathrooms), mid demand (2 – 3 bathrooms), low demand (1 – 2 bathrooms) and portable heaters for travelers in both electric and gas fuel types.

So, read our both tankless water heater guide and reviews and find the best suitable tankless water heater for your home. For easy understanding, we have also provided you with a Comparison Table below with product name, fuel type, major features, flow rate and our rating for the product.

Best Tankless Water Heater Reviews 2018

Product NameType, FeaturesGPMRatingPrice
Tempra 36 Plus - Best Tankless Water Heater
  • Electric
  • Whole House
  • Feature Rich
7.5 GPM 4.5/5 Check Latest Price
EcoSmart ECO 27 - Best value for the Money
  • Electric
  • Value for the Money
6.6 GPM 4.5/5 Check Latest Price
Takagi T-KJr2-IN-NG - Best Gas Heater
  • Natural Gas
  • Indoor
  • Good Pricing
6.6 GPM 4.5/5 Check Latest Price
Rheem RTGH-95DVLN - High GPM
  • Natural Gas
  • Suitable for Large House
9.5 GPM 4.5/5 Check Latest Price
Rinnai RL75iN - Mid Demand
  • Natural Gas
  • High Quality
  • Expensive
7.5 GPM 4.5/5 Check Latest Price
SioGreen IR8000 - No Limescale or Corrosion
  • Electric
  • No limescale, Corrosion, or Sediment
4.6 GPM 4.5/5 Check Latest Price
Titan SCR2 N-120 - Low Cost
  • Electric
  • Low Cost
4 GPM 4.5/5 Check Latest Price
Eccotemp FVI-12-LP - Cheapest Tankless Heater
  • Propane
  • Indoor
  • Cheap
4.8 GPM 4.5/5 Check Latest Price
EcoSmart ECO 11 - Portable Electric Heater
  • Electric
  • Protable
2 GPM 4.5/5 Check Latest Price
Camplux 10L - Portable Gas Heater
  • Propane
  • Portable
2.34 GPM 4.5/5 Check Latest Price

Stiebel Eltron Tempra 36 Plus – Best Electric Tankless Water HeaterStiebel Eltron Tempra Plus 36 kW best tankless water heater

Stiebel Eltron Tempra 36 Plus is the most advanced tankless electric water heater and also the highest GPM producing electric tankless heater. Stiebel is a German company and based in Holzminden and manufactures products related to central heating like heat pumps and water heaters. As good as any German product Tempra 36 plus is also well built with high efficiency, quality, and advanced model.

Self-Modulating Power Technology and Advanced flow rate are the two major technologies you can find in Tempra 36 Plus. Standard Tankless electric water heaters use the max or intended amount of electricity to warm the water irrespective of the flow rate. With Self-Modulating Power technology, the amount of electricity used is adjusted according to the flow rate. Self-Modulating tech reduces the power usage even more, and the heater becomes more efficient.

Similarly, with Advanced Flow Rate, the system regulates the amount of water heated according to the usage. For example, when a house is using three showers at a time which requires almost 7 GPM but if the heater can heat only 6 GPM, then the water rushes through the radiator with not enough temperatures. This is where Advanced Flow rate comes into the picture instead of reducing the temperature it limits the flow rate to 6 GPM so you won’t be receiving cold water anymore.

Stiebel Eltron Tempra 36 Plus had a max flow rate of 7.5 GPM (Gallons Per Minute) and a minimum flow rate of 0.58 GPM. A 7 GPM suffice for a three-bedroom house where you can run three showers and also use a faucet or washer simultaneously. Also, remember the max GPM shown by the companies is for hot regions like Florida, areas with much cooler temperature decreases the GPM of any Tankless water heater model.

Tempra series have five other models with higher and lesser power, they are Tempra 12 PlusTempra 15 PlusTempra 20 Plus, Tempra 24 Plus, and Tempra 29 Plus. Tempra 12 plus produces 2.5 GPM and Tempra 29 Plus produces around 6 GPM. So you can find a lower GPM models in this advanced tankless water heater line up.

The efficiency of Tempra 36 Plus is 99% which means 99% of the total heat produced is used to warm the water. A standard tankless water heater had an efficiency of max 85%. With 99% efficiency, you can save more money on your electricity bill and also be eco-friendly.

It also comes with an analog dial which can be used to adjust the output water temperature between 86°F to 140°F. To make things easier, Stiebel had divided the dial into three ranges hand wash, Residential and Commercial.

The size of the Tempra 36 Plus model is slightly bigger than an average suitcase and mostly fit at any place in your home. It can be installed in your bathroom or under your sink or garage as long as it gets its power source.

Finally, we conclude to say that Stiebel Eltron Tempra 36 Plus is the best whole house electric tankless water heater review we had done with the highest efficiency of 99%, highest GPM of 7.5 in electric tankless heaters and with advanced technology in the market.

7 new from $775.54
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Last updated on November 23, 2017 4:31 pm

EcoSmart Eco 27 – Editor’s Pick (Best Value for Money)Eco Smart Eco 27 best electric tankless water heater

Choosing EcoSmart ECO 27 as the Editor’s Pick is due to its affordable cost with high features, efficiency, and quality. ECO 27 had a patented Self Modulating Technology but also one of the best-selling and top-rated tankless water heater.

Self-Modulating technology increases the efficiency of the tankless heater to 99.8% which is save almost 50% of a traditional tank heater. The technology works as follows, inside the heat exchanger, there are three chambers when the exchanger starts warming the water, the water in the first chamber gets heated up to a specific flow. Once the amount of flow is increased the water enters into the other two chambers. This way the amount of electricity used get decreased significantly. If you would be using your faucet regularly then ECO 27 helps to reduce electricity bill.

Advanced flow rate is the only feature that is lacking in the Eco 27 water heater when compared with the best tankless electric water heater review (Tempra 36kW).

EcoSmart Eco 27 starts at a minimum flow of 0.25 GPM and can produce a maximum of 6.6 GPM. As you know, the amount of GPM varies depending on the temperature of the water that enters the heat exchanger. The amount of GPM mentioned by the companies is of the warm regions like Texas. People living colder areas may get almost half of the GPM shown which in this case will be around 3 GPM at the lowest.

The dimensions of the ECO 27 tankless heater are 17″ x 17″ x 3.75″ and weighs about 13.75 lbs. The compact size of ECO 27 makes it easy to place it almost anywhere in the house. It comes with a digital meter and a dial to adjust the temperature up to 1°-degree variation. EcoSmart had a line-up for the ECO series with lower and higher models ECO 8, ECO 11, Eco 18, ECO 24, and ECO 36. The numbers represent the Kilo Watt for the respective model.

Most electric tankless models are easy to install, and for your warranty to be applicable it is advised to install the heater by licensed personnel. EcoSmart comes with a lifetime warranty, but don’t get deceived by the words. Your unit must be mounted within 30 days of purchase, and warranty registration must be filed and postmarked it within 30 days of purchase. If you don’t follow these steps, you wouldn’t get the lifetime warranty.

Overall at a price of around 500$ for a 6.6 GPM Eco 27 tankless electric water heater is a sweet deal that too with 99.8% efficiency which will save you more money on electricity bill. So, if you are looking for a best electric hot water heater with a GPM of 6, then this is the best tankless water heater you can find.

Last updated on November 23, 2017 4:31 pm

Takagi T-KJr2-IN-NG – Best Gas Tankless Water HeaterTakagi T-KJr2-IN-NG mid demand tankless gas water heater

Takagi is a Japanese Company specialized in manufacturing Hot Water Solutions since 1952. They are the first company to sell the Tankless Water Heaters in the North America. Since then they have been top leaders in the tankless heater segment.

Natural Gas Tankless Water Heaters are best for people who are already having an existing Gas Tank water heater as all the pipes and venting is present. If you are switching from electric to gas, then you will have to change a lot which is going to be expensive. So, do your homework before selecting a tankless water heater.

Tankless gas water heaters costs more than electric tankless water heaters, but you will be saving in the long term if the price of Natural Gas or Propane is less than that of electricity.

Takagi T-KJr-IN-NG is an indoor unit which means it should purchase a vent for exhaust gases, the model also comes in an outdoor model too. Other Takagi T-KJr models are Takagi T-KJr2-IN-LP Propane Indoor Unit, Takagi T-KJr2-OS-NG Natural Gas Outdoor Unit, and the last Takagi T-KJr2-OS-LP Propane Outdoor Unit. Select whichever model suits your need the most. An Indoor Tankless water heater is preferred for people living in cold regions with freezing temperatures. An outdoor unit is preferred for people living in temperate areas and doesn’t require a venting as its already present outdoor.

With a GPM of 6.6 in the warm regions, T-KJr-IN-NG is the best on demand water heater for mid demand houses. 6.6 GPM is sufficient for two to three showers or a two-bedroom apartment. The GPM varies from one area to the other depending on the climate.

The efficiency of a typical tankless gas water heater is between 80 to 85% and Takagi T-KJr-IN-NG is no different. Even though it is less than 99% of an electric tankless water heater, still it is significantly higher than traditional water heaters.

The size of the heater is slightly higher than the electric systems but still a lot smaller than tank heaters. The dimensions are as follows 6.7 x 13.8 x 20.3 inches and weigh around 38 pounds. Users can adjust the temperature using a remote provided in box and temperatures can be adjusted from 99°F to 167°F. Takagi heaters are solidly built and can last for more than 20 years.

Talking about the life the warranty of T-KJr-IN-NG is 10 years for the Heat Exchanger and 5 Years warranty for parts. Takagi T-KJr-IN-NG should be installed by a licensed technician to avail the warranty.

So, at last, we say that Takagi T-KJr-IN-NG is the Best one of all the tankless gas water heater reviews we have done in this list. This is also the best tankless gas water heater you can find on the market at 5 to 8 GPM and costs less for installation for people who are having an existing gas heater.

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Last updated on November 23, 2017 4:31 pm

Rheem RTGH-95DVLN – High-Demand Gas Tankless Water HeaterRheem RTGH-95DVLN Heavy Duty Tankless Gas water heater

Rheem RTGH-95DVLN is the advanced residential tankless gas water heater and best for houses with a very high demand for hot water. The price tag of the RTGH-95DVLN is very high around 1200$, so it is not the best option for small or low demand houses. Even though the price is very high it is a money saver in the long run. The condensing technology in the heat exchanger increases the efficiency of the system from 80% to almost 95% means it will save more money on the gas bill and venting.

So, what is condensing heat exchanger and how does it save money on venting? In a regular gas tankless water heater, the gases which damage the radiator are sent through the exhaust which requires an expensive venting. With this tech, those gases are used to warm the temperature as the inbuilt materials are of high quality. Therefore, it can send the exhaust gases with a regular vent.

RTGH-95DVLN with a 9.5 GPM it can be used as a whole house tankless water heater that can supply hot water to two showers, laundry, faucet, and a dishwasher simultaneously. So, with this unit, you will never run out of hot water and best suitable for 3 or 4 bedroom houses or houses with a high demand for warm water.

Coming to the efficiency as we said above it is 95% efficient due to the condensing heat exchanger. 95% efficiency is the best you can find in a Tankless gas water heater. The unit is also environment-friendly as it releases very low NOx which is a harmful gas released by gas heaters and it is also energy star certified.

Rheem RTGH line-up had both natural gas and propane models with indoor and outdoor units respectively.  Here are the models Rheem RTGH-95DVLN indoor natural gas model, Rheem RTGH-95DVLP indoor propane model, Rheem RTGH-95XLP outdoor propane model and finally Rheem RTGH-95XLN outdoor natural gas model. Buyers can select whichever model they need according to their needs.

Other significant features of the RTGH-95DVLN water heater are it comes with a digital remote to control temperature and for maintenance. This water heater functions above 9840ft which is required for people in high altitude areas. The freeze protection till -30°F allows the unit to run without any problems.

Coming to installation, it should be installed by a qualified expert to avail the warranty. The warranty for exchanger is 12 years, for parts it is 5 years and unusually they are providing warranty for labor for up to one-year.

We conclude that Rheem RTGH-95DVLN is the best gas tankless water heater in 2018 for houses with high demand. If the price of the unit is not a problem, then you should consider this highly rated, well built and efficient gas tankless water heater system.

*Note: A similar model from Takagi T-H3-DV-N, take a glance at it if you are interested in this product.

Last updated on November 23, 2017 4:31 pm

Rinnai RL75iN – Best Mid Demand Gas Tankless Water heaterRinnai RL75iN mid-demand best gas tankless water heater

Rinnai RL75iN is an indoor Natural gas tankless water heater is perfect for houses with 2 to 3 bedrooms. It can be used as both residential and commercial unit, to use as a commercial unit you can purchase a remote controller which will extend the max temperature to 160°F from the residential max of 140°F.

Rinnai RL75iN can produce up to 7.5 GPM which can supply hot water to two bathrooms, one dishwasher or laundry, and a faucet simultaneously, that’s a lot of water flow. Well even though it seems as repeating, the GPM varies depending on the temperature of water reaching the heat exchanger. If the temperature is high more GPM is produced if the temperature is low less GPM is delivered. Make sure you read the Guide below for more info.

In the same series Rinnai RL there are higher GPM versions which provide up to 9.4 GPM at just a few hundred dollars difference. These are the 9.4 GPM models Rinnai RL94iN and Rinnai RL94iP. There are other models in the RL75 series where the energy source is Propane and comes in both indoor and outdoor models. Outdoor models are best for hot climates if vandalism is not a problem and indoor units are best for colder climates.

The efficiency of the RL75iN heater is 0.82 or 82% which is standard as another similar tankless gas unit. Users can also connect it to a recirculation pump if available.

Using the digital meter on the tankless water heater you can adjust the temperature of the water according to your needs. This system had a unique feature; you can connect your heater with Wi-Fi. Using a mobile app provided by Rinnai you can control temperature, do diagnostics, receive maintenance alerts and register the product with Rinnai.

The size of the tankless water heater is 14*9.3*23 inches which can fit in most of the places. Since it’s an indoor unit, it requires a special vent made up of Category III stainless steel.

Finally coming to the installation similar to most of the models Heat Exchanger had a 12 years’ warranty, and 5 years for parts. To avail warranty, you may either need to register the product within 30 days of purchase or should provide a bill with purchase date.

Finally, we would say that this is one of the best tankless gas water heaters in the mid demand range. You may find the cost of the heater to be expensive, but the build quality and service provided by Rinnai are worth the price. It also looks fancier than models from other companies which would be a plus for people with new homes.

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Last updated on November 23, 2017 4:31 pm

SioGreen IR8000 – Maintenance Free Tankless HeaterSioGreen IR8000 maintainance free tankless water heater

SioGreen is the first company to release a Tankless Infrared Water Heater instead of conventional heating coils. Infrared heaters similar to standard electric tankless heaters use electricity to heat water.

People living in hard water or well areas the tankless heaters build limescale over the heating coils which may also cause corrosion of coils. With the patented technology of SioGreen, the coil-less technology heats the water with Quartz infrared energy. Which means the water will never come in contact with the metals in the heater. Therefore, there is no longer a build-up of limescale or cause of corrosion. So, users never need to worry about the maintenance of the tankless water heater.

SioGreen IR8000 can produce hot water of up to 4.6 GPM at 30°F rise in warm regions, and the activation flow is 0.5 GPM. At 4.6 GPM it is suitable for small houses or can use as a commercial tankless water heater for Spa’s, Restaurants and laundry services. With 4.6 GPM you can efficiently use it for two bathrooms simultaneously and suitable for small houses.

The heater also comes with a digital meter where you can adjust the temperature of the output water. Talking of the temperature, the efficiency is one factor to consider. As any other best electric tankless water heaters IR8000 also comes with very high efficiency of 98%.

SioGreen IR series has multiple models with IR8000 being the most powerful; there are six other different models with less GPM. Click this link to check the other similar models. If you are looking for a much smaller maintenance free tankless water heater, then have a look at them.

The product dimensions are as follows 14*6*20 inches and weigh about 28 pounds. The size may seem like more than other models on the list, but actually, it isn’t so big. It can be placed at almost any location with the proper electric source.

Warranty of the SioGreen IR8000 comes with 10 years for heat exchanger and 3 years limited warranty for other parts. People buying from online stores need to register the product within 30 days of purchase.

Conclusion, is it worth to buy? We would recommend it for people living in hard water and well areas, or for people who don’t like maintenance or cleaning. You can see the benefits clearly, no sediment, corrosion, or limescale which also maintains the efficiency for lifelong. It’s clearly the best buy for right usage requirements.

Last updated on November 23, 2017 4:31 pm

Titan SCR2 N-120 – Low-cost Electric HeaterTitan SCR2-N-120 affordable electric tankless water heater

Titan SCR2 N-120 electric tankless water heater is an indoor unit which is very small in size and costs around 250$. Even though it costs less, it can supply 4 GPM of hot water which is considered high for the price.

It is recommended for point of use applications or a small house. As the GPM is only four it is suitable to provide hot water for a single bathroom and a faucet simultaneously.

Titan SCR2 N-120 is also best for people who are already having a whole house water heater and just looking for a bump in GPM. Say if have a 7 or 9 GPM tankless water heater and you only need 2 or 3 more GPM then instead of buying a larger one you can opt for this model.

To discuss more GPM of the Titan SCR2 N-120 the 4 GPM mentioned above is when the temperature difference is 20°F. With the increase in temperature the GPM decreases, for a 40°F rise you will get only 2 GPM, and for 81°F you will get only 1 GPM. Also, the minimum activation flow is 0.5 GPM

The unit is also suitable for warmer regions where the normal water temperature is 70°F. If you are living in colder areas, then this model is not for you.

Surprisingly the efficiency of the unit is almost 99.5% which will save you a lot more money in the long run. Also, the max pressure is 150 psi which means the water would be rushing to reach you. Titan SCR2 N-120 comes with temperature controls on the unit.

Installation of the unit is straightforward if you have an existing setup, the warranty for the heat exchanger is 10 years and for other parts is one year.

Finally, if you are from warmer regions and looking for an electric tankless water heater for a low demand house or as point of use water heater. Then this is the best electric point of use water heater you can find with high efficiency, good GPM, and compact in size.

Last updated on November 23, 2017 4:31 pm

Eccotemp FVI-12-LP – Affordable Gas Tankless Water HeaterEccotemp FVI-12-LP affordable gas tankless water heater

Ecotemp FVI-12-LP is a propane tankless water heater for indoor fitting, comes with a stainless steel ventilation kit, and the best part is it costs less than 300$. So this makes the Ecotemp FVI-12-LP the best affordable gas tankless water heater on the market.

FVI-12-LP can produce hot water of 4.8 GPM at 80psi when the temperature rise is 45°F and decreases with the increase in temperatures. With 4.8 GPM in warmer areas, it is best suitable for small houses with less demand. The minimum activation flow rate is also very high at 0.93 GPM, this may cause you inconvenience during the hand wash.

Efficiency at 79% or 0.79 is less than 0.85 of a standard tankless gas water heater, and this raises the gas bill by 5% than a regular tankless gas heater. If you are shifting from a tank to tankless, then this unit will save money on the gas bill.

The size of the tankless water heater is 6*15*24 inches and weighs 33 pounds, and it is a bit larger than similar range water heater.

It comes with two dials one for the gas regulator and the other for temperature control.

Warranty for the FVI-12-LP propane tankless water heater comes with only two years for both heat exchanger and parts.

Coming to the final part, Ecotemp FVI-12-LP is best suitable for people who are in tight budget and require a tankless water heater. Other than that we won’t recommend this for people looking for a mid-range tankless water heater.

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Last updated on November 23, 2017 4:31 pm

EcoSmart Eco 11 – Portable Electric Tankless Water HeaterEcoSmart ECO-11 Best Portable Electric Tankless Water Heater

Eco 11 is same to same as Eco 27 in functioning as we reviewed above. Except it produces less GPM as it consumes less electricity and compact in size. The compact size is the reason we select this product as a portable electric tankless water heater.

If you are looking for an electric tankless water heater for your RV or camping at the size of 11.5x8x3.75 inches this is the best suitable for you. It weighs less than 7 pounds means you can carry it anywhere with ease. The electrical requirements are 11kw at 220v or 13kw at 240v which are standard requirements for Eco series.

Eco 11 produces at 2 GPM at 40°F temperature rise of water, and with the increase in temperature difference, the GPM also decreases. With correct temperatures, you can have an endless supply of hot water.

The efficiency of the Eco 11 portable electric water heater is 99% which is same as Eco 27. High efficiency means you can save a lot of money on the electricity bill. This high efficiency is perfect for traveling as electricity could be very limited. It also comes with a dial to adjust the temperature of the water.

Eco 11 comes with a lifetime warranty on heat exchanger and all the parts. But, the unit must be installed within 30 days of purchase, and warranty registration must be filed and postmarked it within 30 days of purchase. If you don’t follow these steps you wouldn’t get the lifetime warranty.

Overall, if you are looking for a portable electric tankless water heater with decent GPM and high efficiency, then this is the best tankless water heater for you. The product may seem expensive, but the quality and the features are worth the price.

Last updated on November 23, 2017 4:31 pm

Camplux 10L 2.64 GPM – Portable Gas Tankless Water HeaterCamplux 10L 1 Best Portable Tankless Water Heater

It is the most rated portable propane tankless water heater which is best suitable for RV’s, camping and cabins. It is an outdoor heater but can also be used as indoor provided proper ventilation and works only on LPG. To start the ignition, you either need electricity or 2 “D” cell batteries.

Camplux 10L tankless heater is easy to set up at any place as the size is small with dimensions as follows 12.9 x 8.3 x 21.6 inches. It weighs 18 pounds which may be a little heavy but right to move around in an RV or similar vehicle.

The GPM is 2.64 at a rise of 46°F temperature rise and can rise to 114.8°F which would decrease the outflow. The minimum pressure required to activate the heat exchanger is 3.6 psi.

The unit also comes with excellent safety features, a 20 min automatic safety device, anti-freezing protection, oxygen depletion safety shutoff, and flame failure device.

Camplux 10L comes with two knobs for gas regulation and temperature adjustment. The two would be very handy and turn the gas regulator to zero can provide you with a cold shower.

There are multiple models in the Camplux series like Camplux 5L, Camplux 6L, and Camplux 16L notably. You can select a higher or lower GPM model according to your need.

Coming to the end Camplux 10L portable propane hot water heater for camping or RV is the best option. It had got all the features for a water heater suitable for travelers. If you feel the Camplux 10L isn’t so portable, you can select smaller versions like Camplux 5L or Camplux 6L. The price of the water heater is also reasonable, and it is also rated excellent by many users.

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Buying Guide and F.A.Qs – Tankless Water Heater

There are plenty of features and requirements one needs to know before one consider to purchase a tankless or on demand water heater for your house or needs. That is why we have written this guide to help you understand more about Tankless water heaters.

Difference between a tank and tankless water heater?

Tank water heaters are the traditional water heaters present in most of the houses in the United States. They work by storing the hot water produced in a tank which may vary from 30 gallons to 80 gallons. Tank heaters run throughout the day and provide the hot water whenever required. As they are running 24 hours a day, they consume a lot of electricity or gas which makes them very costly to use.

Tankless water heaters warm cold water on demand as they can instantly heat the water and eliminates the need for a tank. As they use energy only when required, they will save almost 20 to 25% on your electricity or gas bill. They are also very small in size and installation is also similar to tank water heaters.

Hope you have understood the difference between the tank and tankless water heaters.

How much usage will you need?

Amount of hot water used at a time is essential criteria for selecting a tankless water heater.

Unlike tank water heaters where hot water is stored in a tank, tankless water heater heats water when required. The amount of water heated in a tankless heater is measured in GPM – Gallon per Minute. This GPM varies from 1 to 14 GPM for residential tankless water heaters. So you should calculate the highest water usage times in your home before you select a tankless unit. The table below can be useful, check it.

*Note: Also Check “Climate” subheading for more information.

Shower2 GPM
Washing Machine1.5 GPM
Dishwasher2 GPM
Kitchen Sink1 – 2 GPM
Bathtub4 GPM

Using the table, you can quickly calculate when you use the peak amount of hot water. For most of the people you can select by no of bedrooms, for a single bedroom house a 3 to 5 GPM tankless water heater is sufficient. In case of a two-bedroom apartment, 5 to 8 GPM is required, and homes with 3 bedrooms need 8+ GPM whole house tankless water heater. Families with 4+ people or two-story homes prefer to install two 5 to 8 GPM heaters for more ease.

Most models provide GPM charts with more factors like climate and usage. Check the images section or visit the company website for the charts.

Energy Source:

Electric and Gas are the two types of tankless water heaters, both of these vary in many ways like Cost, installation, maintenance, and supply.

Electric Tankless water heater

Tankless electric water heaters work by drawing water into a heat exchanger where a single or multiple chambers heats the water. Electrical units’ costs less than gas models because it doesn’t require a venting system. One disadvantage of electric units is they are not as powerful as gas units which means they provide less GPM. Even on our list, the highest an electric tankless water heater can produce is 7.5 GPM. Whereas the highest GPM by a Natural gas or propane heater is 9.5 GPM. Installation of electric tankless water heaters is straightforward to do and can mount it both outdoor or indoor. Electric heaters are mostly preferred by smaller houses with less or medium water demand.

Gas Tankless Water Heater

Most of the gas tankless water heater have both natural gas and propane variants with outdoor and indoor variants respectively. Gas heaters also work same as electric units except gas units require a venting or drain for exhaust gases. Venting is required for indoor heaters which send the exhaust gases outside, and a drain fo the units with condensing technology units. Venting needs very costly materials which would increase the value of the heater substantially.  However, gas units are more powerful as they have models which can produce up to 10 GPM of hot water. This is the reason why families with high water demand prefer Gas Tankless water heaters and are also chosen for homes in colder regions.

So, which type to choose? People who are already having a working gas heater prefer a gas tankless water heater as the installation process is easy. Homes with less water usage and not having a gas pipe prefer the electric tankless water heaters.

The region you live:

The United States in one of the most diverse country on the planet, the temperature in the Texas vary a lot from the New York. So the temperature of water changes from one place to another which requires more or less energy for a tankless water heater to produce hot water. Most of the GPM produced shown by websites is the GPM produced in hot regions like Texas or New Mexico. For areas in the north of the United States, the GPM drops by almost half, which means a tankless water heater producing 9 GPM in Texas may deliver only 4.3 GPM in New York during winter. So to make things easy most manufactures divide the United States into different zones and shows how many gallons per minute of hot water is produced in those respective regions. Here is an example of a similar infographic.


As you may have already known that a conventional tank water heater had an average lifetime of 10 years and warranty of only 5 years.

However, most tankless water heaters come with a warranty of 5 to 12 years for heat exchanger and 5 years on parts. A licensed personnel should install tankless water heaters for assurance, if not the warranty will be void. The Best Tankless Water Heaters comes with at least 10+ years of warranty for the heat exchanger.


Installation of Tankless water heaters is a very difficult for individuals, most of the times they may damage the product. So all of the tankless water heater manufactures made it compulsory to get heaters installed by a licensed professional. If a licensed person does not install the product your warranty will get void.

Before buying a tankless water heater, buyers need to know where they need to install the heater and which energy source do they need. Therefore, they can make the process of installation easy, for example, if you like to install a Gas heater in your garage you should already need an existing gas pipe otherwise your installation cost going to be higher.

Similarly, if are looking for an electric tankless water heater, then your existing electrical set up in the house may not be sufficient and need to change your system. This may increase the installation costs by a large margin depending on your home.

You can find more information by reading the manuals of the products you like, which provide the requirements for the product.


Maintenance of the tankless gas or electric water heaters is very simple, the only primary task you will deal with is limescale. When the heat exchanger warms the water the minerals present in the water like calcium and magnesium get baked and starts to build up limescale on the walls of heating coils. This decreases the efficiency of the heater over time; you can avoid that by removing it regularly. Regularly in the sense for people living in the areas with hard water need to remove it once in a year and areas with soft water need to remove it every 4 to 5 years.

Other than this you may need to get the tankless water heaters inspected once a year to make sure there is no problem with the heater.

Indoor vs. Outdoor:

If you are looking for a tankless gas water heater, then you have come across indoor and outdoor models. So what are these?

Indoor Gas tankless water heaters require an exhaust vent to remove the gases like Carbon Monoxide which are harmful. Venting is a costly process as the materials are expensive and add up during installation. But for people living in areas where the temperature drops to near Zero cannot place a gas tankless water heater outdoor. So for people who live in places with very low temperatures Indoor Gas tankless heaters are required.

People who live in temperate climates like California and Los Vegas can opt for outdoor units which don’t require venting. Therefore, your installation costs are going to less than that of indoor units.

Advantages and Disadvantages:
Space Saving

Traditional water heaters require large tanks which occupy a lot of space and very unattractive.

Tankless water heaters require very less space and can easily fit in most of the places in your house. A low demand heater comes in size no more than a briefcase, and high demand heaters require less than half of what a tradition water heater requires. Some tankless heaters also look attractive.

Energy Efficiency

Efficiency is another primary reason why people opt for tankless water heaters; they use 80 to 95% of the heat energy produced, unlike the tank heater which barely crosses 65% efficiency. This high efficiency reduces your monthly gas or electricity bill by up to 25% depending on the model and usage.

Continuous Water Supply

In a traditional water heater, the temperature of the water drops after using a full tank.

However, in a tankless water heater, the hot water supply is continuous as long as you require, as they heat water on demand.


Tankless water heaters are considered eco-friendly as they are highly efficient and consume energy only when required, unlike 24/7 running tank water heaters. So, by using a tankless water heater, you are not only be saving your money, and time but also helping the nature.

High Initial Investment

Tankless water heaters cost higher than the conventional water heaters, not only for purchasing but also installation. You may even need to upgrade your electric or gas line to maintain with the consumption of water heater. But, you will be saving up to 25% on your energy bills and in the long run, the heater pays itself as lifespan is also double than the tank heaters.

Cold Regions

People living in areas where the temperature may drop below 50°F the tankless water heaters GPM reduces by almost half. Means if a model had 9 GPM this may decrease to 4.3 GPM for colder areas. This problem is common with any type of water heater, you can install multiple tankless heaters if you are having a high demand like 10+ GPM of hot water at a time.

Large families

A household with more than 4+ bedrooms may not get sufficient warm water when used simultaneously throughout the house. For this, you may need to install multiple tankless water heaters to coup up with the demand.

Frequently Asked Questions (F.A.Q’s):

What is Condensing Gas water heaters?

Regular Gas Tankless Water Heaters require a vent to exhaust the gases produced during combustion. In condensing gas heater, the gases are used to heat the water and once cooled will be converted to liquid and later sent through the drain. This way the efficiency of the heater increases from 83% to 95% saving more money.

Are they Safe?

Yes, they are entirely safe when installed by a professional and maintained regularly.

Do they get Tax Benefits?

Yes, Federal Tax Credits are available for some models thus saving the amount of almost 30%.

What is the lifespan?

If installed and maintained correctly Tankless gas or electric water heaters may last as long as 20 years.

Best Tankless Water Heater Brands?

EcoSmart, Stiebel Eltron, Rinnai, Rheem, Takagi, and SioGreen are the yop rated tankless water heater brands.

Do we get continuous hot water?

Yes, Once you start getting the hot water they will be continuous.

Who makes Rheem water heaters?

Rheem is a Private company in America and Rheem water heaters are made in Montgomery, Alabama plant started in 1971.

Are Tankless water heaters worth the money?

That depends if you have a tank heater and satisfied with it then getting a new one doesn’t worth the money. Best rated tankless water heaters are for those who are looking for a long-term solution as the tankless water heaters reduce your electricity or gas bill by 5 to 10%.

Best Outdoor propane tankless water heater?

Most of the highest rated gas tankless water heaters have different models for natural gas, propane and outdoor, and indoor variants respectively. So find a best gas tankless water heater and find propane and outdoor variant for the model.

What is the best tankless water heater on the market?

To find the answer to this question you have to read the above 6000 words review and guide. Yeah, it’s not possible to tell you the best tankless water heater in less than 100 words unless I know your need.

How big of a tankless water heater do I need?

To know that you need to know how much GPM (gallons per minute)  you would need. We have divided into three ranges Low Demand (3 to 5 GPM), mid demand (5 to 8 GPM) and finally (8+ GPM). Choose the range you need and select the one you need by reading our best tankless electric water heater reviews and gas tankless water heater reviews above.

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John Clark

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