A battery energy storage system, or BESS, is a giant rechargeable battery for the power grid. It stores electricity when generation is high and releases it when demand rises.

Why does this matter? Solar panels make power only when the sun shines, and wind turbines only when the wind blows. But people use electricity after sunset too. Without storage, excess renewable power goes to waste.

A BESS charges during peak production hours and discharges during evening demand. This makes renewable power firmer and more reliable, and helps grid operators manage sudden changes.

India is scaling up fast. Adani Green Energy’s installation at Khavda in Gujarat now holds 6.63 gigawatt-hours, more than half of the country’s operational capacity of about 12.6 GWh. The company calls it the world’s largest single-location battery storage site.

That 6.63 GWh can power about two million homes for a day. It equals the batteries of over 1.5 lakh mid-sized electric vehicles, showing how storage is becoming central to clean energy plans.