Excerpt from the January 9, 2018 Popular Science article:
But any renewable future must include reliable storage that can bank surplus power from wind and solar, and then release it on command. So far grid operators have found two solutions. One is the type of storage found in batteries. Another relies on de facto storage: smart devices that control power demand on appliances, mediating between peak-production and peak-demand times. Lippert and her team are looking at both solutions. In the second bucket, they’ve backed a company called Shifted Energy.
Shifted has retrofitted its grid-interactive devices onto water heaters at Kapolei Lofts, an affordable-housing complex. During the day, when there is excess solar on the grid, the devices can turn on the heaters (when few are at home and using them) to preheat H2O for evening showers. By equipping 1,000 water heaters with these devices, Shifted estimates it is creating up to 3 megawatt hours of storage from the excess solar.