Heat-pump water heaters add 120-volt and smart features

Cohen's basement used to carry a whiff of gas. Now his Reservoir heat-pump water heater lets him breathe easier, he says—and he recommends it to friends buying homes of their own. Around that household change, manufacturers are working through the practical obstacles that still keep the technology from more homes.

The first is the electrical connection. Most heat-pump water heaters use a 240 -volt outlet, but Rheem, A.O. Smith and GE Appliances now produce less-powerful versions for a normal 120 -volt socket. They can work well for households of one to four people that would otherwise need an electrical-system upgrade. GE also offers a flexible-voltage product, which experts say could make emergency replacements much easier.

Space is the other constraint. Most systems need 400 to 700 cubic feet of air around them to pull in heat and transfer it to the tank. Split systems move the heat-pump half outdoors, leaving the hot-water tank indoors; SanCO 2 has sold one for years, A. O. Smith introduced its own in April, and Midea won a national competition this month for a split-system prototype.

Software is attacking wasted energy. Apps from most manufacturers can schedule heating when grid power is cheapest and connect appliances to utility programs such as California's WatterSaver, which rewards customers for reducing use when the grid is stressed. Reservoir and Cala Systems build that logic into onboard computers that learn when a household needs hot water. Cala Systems says it has reduced use of the backup electric-resistance element from 35 % of appliance energy use to 7 % in its units, which have reached nearly 400 units across 36 states. Some users have reported glitches with scheduling systems.

In practical terms, the newer designs can widen the pool of homes that can install a heat-pump water heater: 120 -volt models may avoid an electrical upgrade, split systems may fit homes without enough indoor air volume, and automated controls may reduce reliance on less-efficient backup heating. The price gap remains real. Rheem lists a 50 -gallon heat-pump model at $ 1 , 699, versus $ 799 for a highly rated electric-resistance model, with installation adding $ 1 , 000 to $ 4 , 000 or more depending on the home and local labor. Rebates from $ 150 to $ 4 , 000 continue in some places, while the federal tax credit of up $ 2 , 000 was eliminated last year.