Today, SolarCity—a company that’s grown quickly by installing solar panels for free and charging customers for the solar power—announced a new business that will extend that model to providing batteries for free, too. SolarCity is a rare success story for investors in clean technology, and its business model has sped the adoption of solar panels.

The batteries could help businesses lower their utility bills by reducing the amount of power they draw from the grid. They could also help address solar power’s intermittency, which could prevent it from becoming a significant source of electricity. The batteries are being supplied by Tesla Motors, whose CEO, Elon Musk, is SolarCity’s chairman.