3 Best 27 kW Electric Tankless Water Heaters of 2022
Reviews and Buying Tips

Explore 3 best 27 kW electric tankless water heaters for home use, including buying tips, pros, and cons. Reviews of popular models from Eemax, EcoSmart, and Rheem for efficient water heating in small and large homes.

These small and compact water heaters are recommended for homeowners looking to buy a new or replace an old unit that can heat water on demand and save space and energy.

Our tankless guide doesn't talk only about which make and model to buy but provides detailed information about each and compares the main features, specs, and prices.

Top sellers

If you don't have time to read our detailed guide on how to select the best 27 kW electric tankless water heater and reviews of the top three, check out our selection of the popular models:

  1. Eemax EEM24027 (available on amazon.com)
  2. EcoSmart ECO 27 (available on amazon.com)
  3. Rheem Performance 27 (available on amazon.com)

Eemax EEM24027

EcoSmart ECO 27 Rheem RETEX 27
Phase (Hz) Single Single Single
Voltage (V) 240 240 240
Max amperage (A) 112.5 112.5 113
Circuit breakers 3x40 3x40 3x40
Wire size 3x8 3x8 3x8
Min. water flow to activate (GPM) 0.3 0.3 0.3
Max. water flow (GPM) 6.1 (@30 F) 6.6 (@28 F) 6 (@34 F)
Temperature range (F) 80-140 80-140 80-140
Size (inch) 17 x 17 x 3.75 17 x 17 x 3.75 18-1/4 x 17-5/8 x 3-1/2
Weight (lbs) 13.75 13.75 17.8
Warranty (years) 5/1 Limited lifetime 5/1

What to consider when buying the best 27 kW electric tankless water heater?

There are many advantages to owning one of the best 27 kW electric tankless water heaters reviewed here.

See what to consider when buying one:

Sizing tips

These compact and powerful 27 kW tankless electric water heaters are ideal for point-of-use applications and whole-house water heating that can be used in various applications.

But first, they need to meet specific requirements (see the criteria below).

When sizing a tankless water heater, always consider the flow rate. It shows how many gallons of water can be heated per minute, and it is expressed in gallons per minute - GPM.

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


Energy efficiency (EF) is an essential factor when buying a water heater. The higher the EF is, the less energy you will waste and save more money.

Tankless water heaters are not affected by the stand-by heat loss because there is no storage tank, and water is not heated when not needed. In general, electric tankless models can transfer almost all the available heat to water, which is around 99%.

It is proven that electric tankless models can save energy between 30 and 50%.

Information about annual operating costs can be found in the manual and on the Energy Guide label. 

Note: From the electric water heaters, only heat pump-hybrids are Energy Star approved, tankless is not.

Flow rate

If you are looking to buy a model that can heat and deliver hot water to one or multiple fixtures with the greatest comfort, you will need to calculate the total water flow of devices you expect to use at the same time.

For example, if you want to use a shower with a water flow rate of 2 GPM and a dishwasher with 1 GPM, at the same time, the total flow rate will be 3 GPM. So, you will need a water heater that can deliver at least 4 GPM.

The water flow depends on the temperature rise, which 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.

From this, we can see that if the set temperature is lower and the incoming water temperature is higher, your tankless water heater will produce more hot water flow, and vice versa.

Use this map to find the approximate ground water temperature for the region where you live.


The best electric tankless models are usually equipped with the most advanced features such as self-modulation, quality components, digital temperature control, diagnostics, preset temperatures for convenient selection, adjustable flow control, and other energy-saving options.

Replaceable parts

Almost every component of a tankless water heater can be replaced. This ensures that less waste goes into the landfills and more money stays in your pocket.

This is not the case with the tank-type units where leaky tank cannot be swapped out with a new one.

Endless hot water supply

As we know, electric tankless water heaters are equipped with a few heating elements or chambers where water is heated on demand while passing through. So, as long as there is water coming in and the power is on, water heaters won't run out of hot water. But, keep in mind that if the large volume of water passes through the unit fast and the unit doesn't have enough kilowatts, you will end up with lukewarm water only.

Fresh water

Tankless is designed to deliver fresh water because incoming water is instantaneously heated and delivered to the fixture immediately - never sitting inside the unit.


Small and compact size allows installation not only in large homes but apartments, cottages, garages, bathrooms, kitchens, and tight spaces. They are wall-mounted, freeing up the floor space for other use.


Electric tankless water heaters tend to be less expensive to install than their gas counterparts. There are no gas pipe and venting installations.

What can increase the installation cost is if you have to upgrade your home's electric system.

Electric units also require little maintenance and service less time and labor spent on troubleshooting, diagnosing, and repair, resulting in lower costs.

Note: Since installing and troubleshooting the electrical water heaters can be hard and dangerous even for the handyman, it is recommended to hire a professional electrician.

Eemax EEM24027 - 27 kW

Eemax EEM24027 is a small and energy-saving yet powerful electric tankless water heater, designed for the point of use and whole house water heating, delivering enhanced comfort and performance.

Three high-powered heating elements can generate 27 kW of power for fast water heating. Users can expect water flow of up to 6.1 GPM (@30 F) delivered to 3-4 fixtures simultaneously while reaching high temperatures of up to 140 F.

With the provided advanced features, such as temperature and flow sensors, including the computer control board, Eemax 27 kW can perform as you would expect it and as long as the minimum water flow of 0.3 GPM is met.

This 27 kW unit is equipped with advanced water flow and temperature sensors, and when combined with the microprocessor, your water heater will modulate the power to deliver accuracy and the best comfort. Users can adjust the temperature in increments of 1 F.

Even if running more than two applications at the same time, you should not worry about problems such as when there is not enough hot water or temperature fluctuation.

If you need more information check out our Eemax review.


  • Durable and stylish
  • High efficient
  • Sophisticated sensors and digital temperature control in increments of 1 F ensure accuracy.
  • Computer-controlled modulation to reduce cold water sandwich problem and save energy.
  • Copper and stainless steel guarantee durability.
  • Savings and water flow monitors allow users to see the cost savings and use the information for the best comfort. 
  • It doesn't make any noise
  • Temperature settings: 80 to 140 F
  • 5 years warranty


  • It requires a lot of Amps
  • The operating costs are high
  • Expensive
  • You might need a flow restrictor to ensure the optimal temperature output

Requirements (pdf)

  • Max. amperage draw: 112.5 A
  • Min. required breakers: 3 x 40 A
  • Min. required wire size: 3 x 8 AWG
  • Min. recommended electric service: 300 A
  • Min. flow to activate: 0.3 GPM

EcoSmart ECO 27

EcoSmart ECO 27 is another popular 27 kW electric tankless water heater designed to heat and deliver hot water to a variety of applications in small and large apartments, townhouses, offices, cottages, etc.

EcoSmart is equipped with the three heating elements with the power of 9 kW each, all made of copper, all together delivering the maximum water flow rate of 6.6 GPM (@28 F temp. rise). A lower activation rate of 0.3 GPM also ensures a better user experience.

In addition, these water heaters can determine the appropriate power output using the flow sensors and control board.

Unlike the Eemax warranty of 5/1 years, the ECO 27 model offers a better deal with the limited lifetime warranty. Plus it is cheaper.

We can also see that EcoSmart ECO 27 has the same requirements as the above Eemax model; breakers 3 x 40 A and wire 3 x 8 AWG, including the amperage draw of 150 A and voltage of 240 volts.

For more info about EcoSmart, check out our detailed review.


  • 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 lifetime warranty
  • EcoSmart is part of the Rheem family of brands


  • ECO 27 requires a lot of Amps
  • Higher operating costs

Requirements (pdf)

  • Max. amperage draw: 112.5 A
  • Min. required breakers: 3 x 40 A
  • Min. required wire size: 3 x 8 AWG
  • Min. recommended electric service: 300 A
  • Min. flow to activate: 0.3 GPM

Rheem Performance 27 kW

Rheem Performance RETEX-27 is another excellent device from this manufacturer that can save you up to 50%. This whole-home electric tankless water heater is ideal for families looking for enhanced comfort and convenience and need a unit that can fit in small and tight spaces.

It is an easy-to-use heater meant for both point of use and whole-home water heating, also RVs, mobile homes, and offices, delivering hot water on demand and in endless supply.

Rheem 27 kW is designed to provide hot water with a maximum temperature of 140 F and water flow of 6 GPM (@34 F), but it depends on the incoming water temperature.

Selecting the temperature is very easy as the unit is equipped with an external digital thermostatic control and LED display.

This electric and tankless unit is equipped with three heating elements/chambers, each generating 9 kW, to a total of 27 kW. They are made of corrosion-resistant copper and include a brass top for easy replacement.

Depending on the demand and temperature settings, the unit can modulate the power using the advanced water flow rate and temperature sensors, resulting in optimal performance, and maximized efficiency and cost savings.

According to the provided Energy Guide, Rheem RETEX-27 has an estimated yearly energy cost of $289 (2022), but it depends on your utility rates and use.

Note: If you need a heater for the greater hot water demand than what is presented here, consider electric tankless water heaters with the power of 36 kW, or even gas models, if available to you.


  • Modern metallic look
  • Compact wall-mount design to save space
  • High efficiency (99.8%)
  • Self-modulating power control helps you save energy and reduce temperature fluctuation.
  • Dial Control with adjustable digital temperature display showing output temperature with 1-degree increments.
  • Silent
  • Threaded copper immersion heating elements with brass top for longer life and easy replacement.
  • Temperature settings: 80 - 140 F
  • Field replaceable elements
  • 5-year warranty


  • It requires a lot of Amps
  • Higher operating costs

Requirements (pdf)

  • Max. amperage draw: 113 A
  • Min. required breakers: 3 x 40 A
  • Min. required wire size: 3 x 8 AWG
  • Min. recommended electric service: 300 A
  • Min. flow to activate: 0.3 GPM


With so many makes and models available, choosing the right water heater for your home can be time-consuming unless you analyze and compare the above 3 best 27 kW electric tankless water heaters.

Whether you buy a model from Eemax, EcoSmart, or Rheem, rest assured that you will get a model that can save you energy and water, last for a long time, and deliver plenty of hot water when need it.

And, if you require professional installation, we recommend getting a few quotes from the local experts.