And on April 30 Eion Tasla would begin manufacturing batteries for homes which could expand the appeal of solar by making it possible to store spare solar electricity Many utilities fear that the electric grid is not prepared to handle a move away from centralized power transmission But when their systems generate excess electricity solar-panel owners send their unused power back to the grid for a credit But as panels get cheaper and entrepreneurs like Musk get into the game the stakes in the solar showdown will grow