The humble electric water heater found in 50 million U.S. homes also may be a promising new tool for cutting residential utility bills, promoting clean energy, and strengthening the reliability of the power grid.

A new analysis by the Brattle Group gives a glimpse into just how large of an untapped resource they might be, citing water heaters' ability to interact with the utility grid:

Water heaters are essentially pre-installed thermal batteries that are sitting idle in more than 50 million homes across the U.S. 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 and, in some cases, there may be excess supply of energy from low- or zero-emitting resources such as wind power. Further, recent technological advancements have enabled “grid interactive water heaters” to be controlled over very short time intervals and with near instantaneous response, allowing them to provide frequency regulation and other grid balancing services that are highly valuable in markets with rapid fluctuations in supply.

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