Tankless Water Heaters - Electric

Electric tankless water heaters from 8 kW through 36 kW, at 240V and 208/240V, from single-bath units to whole-house models.

Electrical capacity is what decides whether these are installable, not plumbing. A 27 kW unit draws roughly 113 amps and needs three 40-amp double-pole breakers; a 36 kW unit needs four. On a typical 150-amp residential service that is most of the panel, and many retrofits fail at this point rather than at the pipe.

Sizing follows temperature rise, not gallons. The same unit that delivers 4 gpm in Florida delivers barely 2 gpm in Minnesota, because incoming groundwater is 30°F colder and the element has a fixed kW output. Size from your local winter inlet temperature and the simultaneous fixtures you need to run.

Electric tankless has no venting and no combustion air requirement, which is its real advantage over gas in tight or interior spaces.

Brands include Rheem and Stiebel Eltron.

Smaller 8 to 13 kW models suit a single bathroom or a warm-climate home; 24 to 36 kW models serve a whole house. For a single sink, look at point-of-use water heaters. Compare with gas tankless water heaters, browse all tankless water heaters, and read what size tankless water heater do I need before you order.

Frequently asked questions

What breakers does an electric tankless water heater need?

It depends on the kW rating. A 27 kW unit draws roughly 113 amps and needs three 40-amp double-pole breakers, and a 36 kW unit needs four. Check your panel before you order.

What size electric tankless heats a whole house?

24 to 36 kW models serve a whole house, such as the Rheem RTEX-27 and RTEX-36. 8 to 13 kW models suit one bathroom or a warm-climate home.

Is there a 120V electric tankless water heater?

Yes, for a single sink. Point-of-use units such as the Rheem RTEH3512 run on 120V. See point-of-use water heaters.