Best Whole House Electric Tankless Water Heater

Get stuck in searching for the best whole house electric tankless water heater. It is hard for an electric unit to keep up during the cold winters when the temperature drops below freezing. That’s why if you are living in a cold climate and demand hot water then I recommend a whole house electric tankless water heater instead of the natural gas water heater. The whole house water heater is the best choice if you are living in the southern area where the temperature is high.

Then, we recommend you to look at these models:

1.Ecosmart ECO 27

Ecosmart is one of the popular water heater brands. It gives a wide range of models with different capacities and sizes according to your demand. Ecosmart ECO 27 kW is the second most powerful Electric Tankless Water Heater. 

If you live in colder climates where the groundwater temperature is as low as ~42°F, you should expect no more than 3-3.5 GPM. In our testings and feedback from the owners show that the real maximum flow rate is about 5.6 GPM in warmer climates. But according to the manufacturer, it can provide up to 6 gallons of hot water per minute

EcoSmart has 6 tankless heaters in their ECO line-up. If you live in a particularly cold area, it may be wise to consider purchasing the more powerful ECO 36 as it offers a higher flow rate. Similarly, if your household has a lower water consumption and the inlet temperatures are generally higher, going with ECO 8, 11 or even 18 may be the better choice for you.

ECO 27 is an excellent choice for someone wanting to save money.

  • Maximum Flow Rate: 5GPM
  • Activation Flow Rate: 0.25 GPM
  • Dimension: 17″H x 17″W x3.75″D
  • Service Requirements: 113 amps (3 double pole x 40 amp breakers) 99.8 Energy efficient.


  • Easy to operate
  • Adjustable and highly accurate temperature control
  • Small physical size


  • Warranty condition

2. Stiebel Eltron Tempra 24 Plus

Tempra 24 is a German Brand. Stiebel Eltron Tempra 24 Plus is a whole house electric tankless water heater. It is best for homes with 2 bathrooms.

One special thing about this water heater is its Advanced Flow Control technology. It makes sure that when the hot water demand is higher than the unit can typically handle, it prevents the shower or the appliances to get cold water by reducing the pressure and keeping the water hot.

You will get a higher flow rate using more power consumption but you will have to make sure that there is enough liquid to start it running. It is designed to use in two flow rates:-

  • For 240 Volts.
  • For 208 Volts.

In technical specifications, it’s able to provide 1.5 to 4.5 GPM of hot water depending on the temperature rise. 

Stiebel Eltron Tempra 24 Plus draws 100 amps and requires 2 double poles 50 amp breakers. One breaker with 2 live wires and a ground. And the other breaker with 2 live wires. No neutral wire is needed. Make sure you have enough space in the panel.

It also saves you a huge amount of space compared to traditional storage water heaters.

We would recommend you to buy this whole house electric tankless water heater for a 1 or 2 bathroom home or apartment.

  • Maximum Flow Rate: 4.5 GPM
  • Activation Flow Rate: 0.5 GPM
  • Dimension: 4.63 x 16.63 x 14.5 inches
  • Service requirements: 100 amps (2 double pole 50 amp breakers)


  • Stable Temperature Output
  • Unique Tempra Advanced Flow Control
  • Convenient Digital Display


  • If not properly sized may cause pressure drops

3. Rheem RTEX-24

Rheem is an American water heater brand. It offers several models of electric water heaters of different sizes. Rheem RTEX-24 is the second largest model. It can be used as a whole house electric water heater. Rheem RTEX-24’s flow rate ranges from 1.5 GPM to up to 5.7 GPM depending on the temperature rise. 

 It is a perfect choice for a household with lighter hot water demand. If you have three or fewer people at your place, RTEX-24 would be a good fit.

Rheem RTEX-24 draws 100 amps. It has three heating chambers so you would need 3 double poles 40 amp breakers. I imagine you should have at least 150 amp service to be able to safely run this whole house electric tankless water heater.

If you’re sure about this model, we recommend you to purchase this model. 

  • Max. Flow Rate: 5.7 GPM
  • Activation Flow Rate: 0.3 GPM
  • Dimensions: 4 x 18 x 19 inches
  • Service Requirements: 112 amps (3 double poles 40 amp breakers) can replace a 40-gallon storage-tank water heater.


  • Very accurate digital controller
  • Saves space
  • Unlimited hot water
  • American brand


  • Costly

4. Bosch Tronic WH27 6000C

This model is a whole house electric water heater but at the same time, it’s best suited for smaller households, office suites, and garage apartments. Meaning that you shouldn’t use it for more than 1 or 2 applications at a time. The activation flow rate here is at 0.8 GPM. The flow rate of the Bosch Tronic 6000 C ranges from 2 GPM to 3.5 GPM. It requires 3 double poles 40 amp breakers and may draw up to 120 amps at full load.

The average shower head flow rate is at ~2 GPM. In real life, it means that if you half-open the tap, Bosch wouldn’t ignite and run and you’ll get cold water from your tap. To get it to work and heat the water you’re going to need to run it full open.

We’d say that Bosch Tronic 6000 C is an OK whole house tankless water heater if you’re living in a smaller household of 2 or 3 people and the hot water demand isn’t very high.

  • Max. Flow Rate: 3.5 GPM
  • Activation Flow Rate: 0.8 GPM
  • Dimensions: 15.5 x 4.5 x 12.5 inches
  • Service Requirements: 112 amps at full load (3 double pole 40 amp breakers) 97% efficiency.


  • Reliable brand
  • Compact sizes
  • Excellent customer service


  • High activation


What size electric tankless water heater do I need for the house?

You’ll need to raise the incoming water temperature from 40 degrees to 105. You’ll need to be able to heat at least 5.2 gallons of water. So you’ll need a tankless water heater that can produce at least a 60-degree rise in temperature at 5.2 gallons per minute.

Do tankless water heaters work for large homes?

Rinnai V series HE tankless heater is made by Rinnai which is among the oldest tankless water heater makers in the world. So what makes this water heater an ideal option for large homes is because it can provide a large amount of hot water in a short time. Its flow rate ranges 5.3GPM, 6.5GPM, 7.5 GPM and 9.4GPM.

Are there any special requirements in the home to install an electric tankless water heater?

Whether you choose a natural gas or propane tankless water heater, a home heating expert will need to ensure your home can easily accommodate a tankless water heater since tankless water heaters have special venting and gas line requirements. The installation of any gas appliance must be performed by a licensed technician.

How much tankless water heater save me?

The amount you save will depend on how much water you heat, what type of tankless water heater you choose and how efficient the water heater you are replacing is. Generally, depending on equipment efficiency and your family size and usage, a tankless heater can mean hundreds of dollars saved over the unit’s lifetime, compared to a standard tank.

Will an electric tankless water heater work on my current electric system?

Electric Tankless water heaters usually require substantial and expensive upgrades in your system. The Seisco Model RA-28 for instance has four 7,000-watt elements for a total electrical load of 28,000 watts. This extra load requires at least 120 amps.

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