Battery Backup for Rooftop Solar Power Systems Too Costly

Using batteries to retain energy from rooftop solar systems will be too expensive for at least two years, according to industry executives.

That means homeowners who add solar panels to save money on utility bills will continue to lose electricity during blackouts, even after an 80 percent decline in battery costs over the past decade.

Residential solar systems typically send power to the grid, not directly to the house, and don’t run the home during a blackout. For batteries to save consumers money, stored energy must be drained daily, said Jamie Evans, who runs the U.S. Eco Solutions unit for Panasonic Corp., which supplies lithium-ion cells for Tesla Motors Inc.

“Solar will need storage for grid stability,” Evans said yesterday in an interview at the Solar Power International convention in Las Vegas. “Battery costs need to come down and regulatory structures have to change to really scale up.”

As residential solar become more common from California to New York, utility grids will increasingly become stressed without storage to ease supply and demand imbalances, he said.

For now, that means battery storage only makes economic sense for large businesses that get hit with extra fees when their power usage exceeds utility expectations.