In this April 20, 2015 photo, David Cunningham shows a prototype Tesla battery system that powers his Foster City, Calif. home. Cunningham installed a Tesla battery late last year to pair with his solar panels as part of a pilot program run by the California Public Utilities Commission to test home battery performance.
In this April 20, 2015 photo, David Cunningham shows a prototype Tesla battery system that powers his Foster City, Calif. home. Cunningham installed a Tesla battery late last year to pair with his solar panels as part of a pilot program run by the California Public Utilities Commission to test home battery performance. Jeff Chiu AP
In this April 20, 2015 photo, David Cunningham shows a prototype Tesla battery system that powers his Foster City, Calif. home. Cunningham installed a Tesla battery late last year to pair with his solar panels as part of a pilot program run by the California Public Utilities Commission to test home battery performance. Jeff Chiu AP