Intermittent PV and wind often generate amounts of electricity that exceed demand. 100s of MW of batteries are being deployed to shift this excess to other times when demand for power exceeds capacity. Batteries are generally used to bridge this demand and supply gap for short periods, typically 30-60 minutes. But as more and more PV and wind are added to the system, the gap lengthens. Today, 4 hour-capacity batteries are increasingly used, yet the length of these gaps will continue to grow.