When heat-pump water heaters (HPWHs) first gained popularity in the mid-2010s, the available models required 30A, 240V electrical circuits. During normal operation, the highly efficient heat-pump mechanism, which draws only 400W–500W, captures heat from the air and transfers it to the tank. But during periods of high demand, 4500W resistance elements similar to those in conventional electric tanks can energize to boost hot water production. Although users can disable these resistance elements by setting their HPWHs to “heat pump” or “efficiency” mode, the circuit feeding the unit needs to accommodate the full load. It must also be a “dedicated circuit” serving only the water heater.

These requirements are identical to those of most conventional electric tank-style water heaters, making retrofits of existing electric water heaters relatively straightforward. The HPWH’s physical size, airflow requirements, noise, sound, and cooling effects must also be considered, but the critical electric infrastructure is already in place.

Barriers to a gas water-heater replacement

In contrast, replacing a natural gas, propane, or oil-fired water heater with a 240V HPWH generally means installing a new circuit. This can present multiple barriers for customers looking to electrify their water heating: