India plans to make it mandatory for electricity distributors to buy some energy storage capacity as part of their renewable purchases, as the government seeks to curb clean power wastage.

Details of the policy, including how much storage distributors will be required to buy, are still being discussed, Power Secretary Pankaj Agarwal said on Thursday. The government plans to finalize the rules by March, he said at the Bharat RE Summit in New Delhi.

The mandate aims to boost investment in batteries that can store surplus electricity and release it when supplies tighten. Solar generation peaks during the day while wind output fluctuates with weather conditions, leaving the grid with too much power at some times and shortages at others. Without sufficient storage, grid operators can be forced to curtail renewable output.

About 11% of solar power generated in India during the hottest months this year was lost to grid curtailments, even as demand hit a record.

The move follows a government decision Wednesday to offer capital subsidies for energy storage projects, including batteries, pumped hydropower and emerging technologies. India currently has an advisory for renewable energy developers to integrate storage into their projects, and that requirement will now be made mandatory, Agarwal said.

Storage systems have become increasingly important for the global energy transition to make optimal use of clean power as grids struggle to keep pace with the rapid expansion of solar and wind fleets. Energy storage can help make better use of existing transmission lines and reduce the need for investment in new infrastructure.