Water Heaters as Energy Storage a Significant Potential Grid Resource

Smart, grid-connected electric water heaters represent a promising possibility for a more efficient, more economic, and ultimately lower-emissions electricity system. Given that water heating represents more than 15 percent of household energy use, this is a great opportunity to cut energy waste and also the emissions from electricity generation.

New grid interactive water heaters also can be controlled over short time intervals and with near instantaneous response, allowing them to provide frequency regulation and other grid balancing services that deliver value in markets with rapid fluctuations in supply.

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.

A thermal storage strategy, Brattle Group said, can increase benefits relative to the peak shave strategy, at little incremental cost, if offered to customers with larger water tanks in market conditions with a significant price differential between peak and off-peak periods. A fast response strategy, Brattle Group added, can increase benefits over the other two load control strategies in markets with a need for resources that can quickly ramp load up and down.

The industry can be encouraged by the changing perceptions about energy storage technologies and the continued recognition of storage as a critical grid resource. It has become widely accepted that the country needs a more sustainable, more flexible, and smarter grid. Industry has only just begun to recognize that energy storage can provide this smarter and more sustainable solution.