China is rushing to build battery-storage systems to allow electricity grids to cope with rapid increases in intermittent power generation from wind and solar farms. But to truly capitalize on the technology, it needs to ensure they’re used more frequently.

China’s new energy storage capacity, a segment dominated by lithium-ion batteries, jumped to 44 gigawatts at the end of June, a 40% increase from the start of the year, according to National Energy Administration data. That’s already surpassed the nation’s 2025 target and helped fuel a global boom, with energy storage overtaking electric vehicles last year as the fastest growing market for batteries.

Costs, meanwhile, have fallen to the point where the combined expense of generating solar and storing it is almost cheap as coal, according to SooChow Securities.