The Best 36 kW Electric Tankless Water Heaters of 2022 - Review and Buying Tips

Check out our in-depth review of the best 36 kW electric tankless water heaters and buying tips to find the model that fits all your water heating needs, as you would expect.

Water heaters with the energy output of 36 kW are among the most powerful and popular models that you can buy for heating domestic water in residential homes.

Electric tankless heaters are relatively affordable, small, easy to install, and capable of delivering hot water continuously, on-demand, and with significant savings, making them a favorite choice of many.

Top sellers

If you don't have time to read our detailed guide on how to choose the best 36 kW electric tankless water heater and models' reviews, check out our selection of the top sellers:

1. Stiebel Eltron Tempra 36 kW (available on amazon.com)
2. EcoSmart ECO 36 (available on amazon.com)
3. Rheem Performance 36 (available on homedepot.com)

What to consider when buying the best 36 kW electric tankless water heater

Electric tankless water heaters reviewed here are also known as on-demand heaters as they provide hot water only when needed, and in an endless supply. As opposed to traditional tank type, tankless doesn't utilize a storage tank so there is no standby heat loss.

Whether you are buying the cheapest or the most expensive 36 kW electric water heater, note that we are talking about powerful, whole-house heaters that might require you to meet certain requirements before the installation (see the requirements below).

Note: As the installation and repair of the electrical devices can be dangerous for an unqualified person, the recommendation is to hire a professional electrician.

Sizing tips

Check below the average usage in gallons per minute by application:

• Standard sink - 0.5 GPM
• Washing machine - 1 to 1.5 GPM
• Dishwasher 1 to 2 GPM
  
• Shower head - 2 GPM
  
• Whole house - up to 6 GPM
  

Efficiency

Buy a water heater with the highest energy efficiency as it guarantees maximized energy and cost savings. In general, electric models come with the efficiency of around 99% so almost all heat from the heating elements is passed to the water.

Important information such as the water flow, efficiency, warranty, annual operating costs for your particular model, and others can be found in the manual and on the Energy Guide label.

Note: Electric tankless water heaters are not Energy Star approved. If you are looking for electric heaters that are Energy Star compliant check out heat pumps, also known as hybrids.

Flow rate

The flow rate and temperature rise are two important factors that you need to know to properly size a water heater and get the right amount of hot water when needed.

To calculate the total water flow, first make a list of all hot water devices that you might use simultaneously, and add up their flow rates.

So, if you often run one device with 1 GPM, another with 2 GPM and the third one with 3 GPM, the total flow rate will be 6 GPM.

Temperature rise can be calculated by subtracting the incoming cold water temperature from the set outgoing hot water temperature.

So, if the incoming water temperature is 50 F and desired temperature is 120 F, the temperature rise is 70 F.

Note that if the water flows faster or incoming cold water temperature is lower, the outgoing water temperature will be lower.

Use this groundwater temperature map which can help you find the corresponding GPM and approximate usage for your area. As the water flow (GPM) is impacted by the incoming water temperature, a model you chose for the southern region might not be fitted for norther areas.

Use the manufacturers' temperature rise vs. flow rate charts (such as this one from Stiebel Eltron) to see which model and size is suitable for your area.

Features

The most advanced electric tankless models are usually equipped with the most innovative features such as the auto-modulation, copper and stainless steel components, digital display, preset temperatures for convenient selection, adjustable flow control, and other energy saving options.

Stiebel Eltron Tankless Heater – Tempra 36 Plus

Stiebel Eltron Tempra 36 Plus is the powerful electric tankless water heater that can heat water with the power of up to 36 kW, deliver hot water with the maximum temperature of 140 F and water flow of 7.5 GPM (@30 F temp. rise).

Thanks to the provided innovative technologies, including temperature and flow sensors, and a microprocess control, Tempra can deliver superior performance and high efficient heating, anytime.

And with the continuous monitoring, constant adjustments, and temperature accuracy, there will be no more cold showers, temperature fluctuation, or lack of hot water.

Taking into account that we need approximately 2 GPM for a shower, we can see that Tempra 36 Plus can easily supply hot water to three showers working at the same time.

Even with two or more applications running at the same time, users should not worry about the cold-water sandwich problem or temperature fluctuation. The unit is equipped with the self-modulating system which allows water flow and temperature adjustments when needed, and advanced flow control function for the enhanced comfort. If you need more information about Stiebel Eltron, see this review.

Pros

• Modern look
• High efficient
• Increased water flow and advanced control to keep the temperature constant.
• Auto-modulation to reduce fluctuation and save energy.
• Advanced electronics includes digital display, pre-set buttons, and water flow control for more savings and convenience.
• Savings and water flow monitors allow users to see the cost savings and use information for the best comfort. 
• Silent operation (no moving parts, blower, and mechanical switches).
• Temperature settings: 68 to 140 F.
• To prevent scalding you can limit the maximum hot water temperature to 109 F.
  
• 7 years leakage warranty
• Stiebel Eltron is the leader in tankless technology with over 90 years in the industry.

Cons

• It requires a lot of Amps
• The operating costs for any electrical device is higher that its counterpart - gas
• Expensive

Requirements (pdf)

• Max. amperage draw: 150A
• Min. required breakers: 3 x 50 A
• Min. required wire size: 3 x 8/2 AWG
• Min. recommended electric service: 300 A
• Min. flow to activate: 0.77 GPM

EcoSmart ECO 36

EcoSmart ECO 36 is another popular 36 kW electric tankless water heater designed for efficient point of use and whole-house water heating. This small but powerful water heater has a modern and sleek design which makes it suitable for installation anywhere inside the large or small apartment, house, cottage, or office.

When comparing to the above Tempra 36, we can see that EcoSmart ECO 36 has different requirements; breakers 4 x 40 A and wire 4 x 8 AWG, while the amperage draw of 150 A and voltage of 240 volts are the same.

EcoSmart has higher maximum water flow rate of 8.7 GPM (@28 F temp. rise), and lower activation rate of 0.3 GPM vs. 0.77 GPM found on Tempra, and that ensures better user experience.

As opposed to the Tempra warranty of 7/3 years, ECO 36 model offers a better deal with the limited lifetime warranty. Plus it is cheaper.

This water heater comes with the front round knob for the temperature adjustments and digital display. For more info about EcoSmart, check out our detailed review.

Pros

• Modern look
• Compact design saves space
• Energy efficiency: 99.8%
• Self-modulating technology to reduce fluctuation and save energy
  
• Includes digital display showing output temperature
• Silent operation (no moving parts, blower, and mechanical switches)
  
• Temperature settings: 80 - 140 F
• Field replaceable elements
  
• Limited life-time warranty
• EcoSmart is part of the Rheem family of brands

Cons

• ECO 36 requires a lot of Amps
• Higher operating costs

Requirements (pdf)

• Max. amperage draw: 150A
• Min. required breakers: 4 x 40 A
• Min. required wire size: 4 x 8 AWG
• Min. recommended electric service: 300 A
• Min. flow to activate: 0.3 GPM

Rheem Performance 36 kW

Rheem Performance 36 kW water heater is an energy efficient model that can save you up to 50% on water heating costs.

This water heater has an attractive modern metallic look that makes it a nice addition whether you need it for an apartment, house, cottage, or business.

Small and compact design of approximately 18 x 22 x 3.5 inches and weight of close to 23 lbs. makes installation inside the cabinet or under the sink simple, including tight spaces - where other tank-type models cannot fit.

When comparing to the above Tempra 36, we can see that Rheem Performance 36, so as EcoSmart ECO 36, has different requirements; breakers 4 x 40 A and wire 4 x 8 AWG, while the amperage draw of 150 A and voltage of 240 volts are the same.

The maximum water flow rate is 8 GPM which is lower than what we see on EcoSmart and higher then the rate on Tempra.

Except the whole-house application, Rheem is also great for point of use service and small jobs due to low activation rate of 0.3 GPM, which is better than what Tempra offers.

As opposed to the Tempra warranty of 7/3 years, and limited lifetime warranty of EcoSmart ECO 36, Rheem offers "only" 5 years. Plus it is the cheapest of all. This is also the best selling model on the homedepot.com site.

Pros

• Stylish metallic look
• Compact design saves space
• High efficiency
• Self-modulating technology helps you save energy and reduce temperature fluctuation
  
• Includes digital display showing output temperature with 1-degree increments
• Silent operation (no moving parts, blower, and mechanical switches)
  
• Temperature settings: 80 - 140 F
• Field replaceable elements
  
• 5-year warranty

Cons

• It requires a lot of Amps
• Higher operating costs

Requirements (pdf)

• Max. amperage draw: 150A
• Min. required breakers: 4 x 40 A
• Min. required wire size: 4 x 8 AWG
• Min. recommended electric service: 300 A
• Min. flow to activate: 0.3 GPM

Conclusion

The best 36 kW electric tankless water heaters are efficient, reliable, technologically advanced, and can provide ample hot water from one to multiple showers.

Each model from Stiebel Eltron, EcoSmart, and Rheem can be used in variety of applications, including smaller apartments, cottages, and workshops, as an addition, for point of use service, or whole house water heating.

And when professionally installed they can last for a long time and potentially cut your energy bill by 30-50%.

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