In Germany and Australia, homeowners with a battery from Sonnen--which stores energy from rooftop solar panels--no longer have to use a traditional electric utility. When the battery stores more energy than a home needs, it's fed into a virtual energy pool with every other home with the same type of battery, and the community shares energy between homes. In 2017, the company began working with a new development in Arizona that will use a similar "virtual power plant" on 4,000 homes, in partnership with a local utility. While home solar power on its own can sometimes add stress to the grid, a network of homes working together supports larger infrastructure. "It becomes this incredible vision of how renewable energy can take over the grid," says Blake Richetta, the company's North American VP of sales.