"[W]e’ll never build enough batteries to back up the grid. Batteries are costly to build and costly to operate, since energy is dissipated each time they are charged and discharged. Transmission moves power more efficiently. Complementary resources smooth out supply. Demand flexibility narrows gaps and surpluses between supply and demand. The more robustly we deploy complementary resources, transmission, and flexibility, the less storage we will need to build and the less often we will have to deploy it, reducing the overall costs of electricity."