If you were building an electrical grid from scratch (with no regard to regulations or finance), then long-duration energy storage would be a requisite. It just makes sense — store energy when it’s cheap and/or abundant, and discharge when the price is high, or the energy is needed by the grid. Use it to load-shift, peak-shift and smooth; to replace fossil-fuel-fired peaker plants; and to integrate intermittent renewable resources onto the grid.

Long-duration storage fits in with what utilities, independent system operators, and regional transmission operators understand. “Most utilities seem to want much longer-duration storage systems, with 6 to 12 hours discharge, to do serious load-shaping over the day,” suggests an analyst at a U.S. energy think tank. Some of these expectations are being driven by the performance of pumped hydro, once the only source of grid-connected storage.

Economically viable long-duration energy storage could accelerate solar and wind penetration, grid resiliency, and serve to stabilize volatile energy prices. But, long-duration energy storage will not become pervasive until regulators adapt to the capabilities of the technology.