The Tamil Nadu government has mandated battery storage for every new solar project with a capacity of 1 MW or more under its Battery Energy Storage System (BESS) Policy 2026. The policy aims to create 10 GWh of storage capacity by 2029, improve grid stability, support reliable peak-hour supply and increase the use of renewable power. New solar projects must install storage equivalent to at least 10% of their installed capacity, with the systems capable of discharging for four hours. The requirement applies to projects applying on or after the policy notification date and to projects commissioned from April 1, 2027. New substations pooling renewable power must install standalone storage equal to at least 10% of their sanctioned capacity. Existing substations must add storage equivalent to 5% in 2027-28 and a further 5% in 2028-29, as the state currently cannot utilise around 3,000-4,000 MW of solar power during the day. Tamil Nadu Power Distribution Corporation will procure 2,500 MW, or 10,000 MWh, of battery storage in the first phase through competitive bidding. The prices will require approval from the Tamil Nadu Electricity Regulatory Commission, while Tamil Nadu Green Energy Corporation will act as the nodal agency for implementing the policy. The policy covers standalone storage facilities, systems integrated with solar and wind projects, and installations supporting transmission and distribution networks. Existing solar and wind projects can add storage without further approvals, while eligible projects commissioned during the policy period will receive a 10-year waiver of wheeling and transmission charges if the discharged energy is used within the state. The government has also launched a renewable energy application portal covering solar, wind, hybrid wind-solar and battery storage projects. Developers can register, submit documents, pay fees, complete technical scrutiny, undertake load-flow studies and obtain grid connectivity approvals online, while also tracking applications, correcting deficiencies and downloading approval orders.