Home water heaters could be a great opportunity for electrical utilities to add behind-the-meter storage and bring more distributed renewable energy onto the grid, according to a Brattle Group report produced for the Natural Resources Defense Council, the National Rural Electric Cooperative Association, and the Peak Load Management Alliance.

“Electric water heaters are essentially pre-installed thermal batteries that are sitting idle in homes across the U.S.,” the report states. “By heating the water in the tank to store thermal energy, water heaters can be controlled in real time to shift electricity consumption from higher-priced hours when less efficient generating units are operating on the margin, to lower-priced hours when less costly generation is operating on the margin.”

In some cases, it adds, “there may be excess supply of energy from low- or zero-emitting resources, such as wind power,” that often produce cheaper power than competing fossil plants.

Minnesota-based cooperative Great River Energy already manages a “community storage” program that stores a gigawatt-hour of energy each night, using electric resistance water heaters that belong to its 65,000 members, Renewable Energy World reports. “At Great River Energy, we believe there’s a battery hidden in basements all across our service territory,” said Member Services Director Gary Connett.

“When the wind is blowing or the sun is shining, large-capacity water heaters can be enabled to make immediate use of that energy to heat water to high temperatures,” he noted. “The water heaters can be shut down when renewables are scarce and wholesale costs are high.”