On 21 May 2026, India’s grid met its highest demand ever: 270.8 gigawatts (GW) at 3.45 pm (Grid-India daily report for 21 May 2026). Grid-India, the Grid Controller of India, runs the national grid and counts 6 am to 6 pm as solar hours.
The record came in the afternoon, when the sun was doing a lot of the work. The harder moment came later. At 10.45 pm demand was still 252 GW, solar was at zero, and the grid fell 2.6 GW short, against 0.2 GW short at the afternoon peak (same report). That evening gap is what this explainer is about.
Solar’s rise is real
Solar produced 9.4% of India’s electricity in 2025, and its output grew 37% in that single year, according to Ember, an energy think tank (Ember country data and Global Electricity Review, 2026). Clean sources supplied 27% on Ember’s calendar-year count (the Central Electricity Authority’s financial-year figure for FY2025-26 is 29%, the number on our home page), coal generation fell 2.9%, and all of the year’s extra demand was met by clean power (Ember country data, 2026). By 31 January 2026 India had 1,40,602 megawatts (MW) of solar, 27% of all installed capacity, after adding nearly 35,000 MW in ten months (Ministry of Power reply in Parliament, March 2026).
What the record day looked like
| Time | Demand met | Solar | Thermal | Hydro | Wind | Storage |
|---|---|---|---|---|---|---|
| 12.15 pm | 251.5 GW | 80.1 GW | 140.8 GW | 12.6 GW | 9.5 GW | 0 |
| 3.45 pm | 270.8 GW | 60.0 GW | 171.7 GW | 16.0 GW | 13.7 GW | 0 |
| 8.00 pm | 246.0 GW | 0 | 181.6 GW | 28.6 GW | 19.8 GW | 2.6 GW |
| 10.45 pm | 252.0 GW | 0 | 184.3 GW | 28.6 GW | 21.2 GW | 4.2 GW |
Source: Grid-India daily report for 21 May 2026, 15-minute data. Thermal excludes gas, listed separately. Storage means pumped hydro and batteries. Rooftop solar and captive plants are not counted.
At 12.15 pm solar supplied close to a third of everything generated. Across the whole day, though, coal supplied 68% of the electricity, renewables 17% and hydro 9% (same report).
Why the evening falls to coal and hydro
Solar slid from 60 GW at 3.45 pm to zero by 7.30 pm, while demand stayed around 245 to 252 GW. Something had to replace 60 GW in under four hours.
Hydropower, which is flexible (Ember, January 2026), more than doubled from midday to night. Coal did most of the rest, climbing from 140.8 GW to 184.3 GW (Grid-India).
This is not a one-day pattern. On an average day in the first half of 2026, fossil generation fell to 125 GW at 1 pm and rose to 174 GW at 7 pm, a swing of nearly 50 GW. Between 5 pm and 7 am it averaged 168 GW, 22 GW more than in the first half of 2023 (Ember, August 2026). Solar is cutting coal at midday while night-time coal use keeps rising.
Coal holds the evening because it can be dispatched when needed and the fleet is large: 2,21,210 MW in January 2026, or 42.5% of installed capacity (Ministry of Power reply in Parliament, March 2026). But it is hard to turn down. Coal plants must run above a minimum load, set at 55% of capacity for central government plants, or shut down for hours, so operators keep enough coal running through the afternoon to be ready for the evening. When midday demand is weak, solar gets cut instead: about 2.3 terawatt-hours (TWh) between late May and December 2025 (Ember, January 2026).
Prices show the same pattern. On the power exchanges, prices averaged ₹2.84 a unit in solar hours (9 am to 5 pm) and ₹6.36 in the evening peak (5 pm to midnight) across 2023-24 and most of 2024-25, according to the Maharashtra Electricity Regulatory Commission (MERC tariff order, March 2025). That gap between cheap afternoons and dear evenings is what storage is built to close.
What is being built for the evening
Batteries. The Centre is providing viability gap funding, a government grant towards building costs, for 43.8 gigawatt-hours (GWh) of battery storage (Ministry of Power reply in Parliament, July 2026). The national electricity plan puts the need at 34 GWh by 2026-27 and 236 GWh by 2031-32 (the 2025 funding guidelines cited an earlier estimate of 37 GWh by 2027), and the Central Electricity Authority has advised solar plants to add storage equal to at least 10% of their capacity, for at least two hours (same reply). Progress is visible: Ember counted 0.5 GWh of operating batteries in January 2026, and by June reported a single 3.37 GWh project at Khavda in Gujarat, built within 10 months (Ember, January and June 2026). NTPC, the government-owned power producer, has tendered 1.7 GW of batteries at 11 of its coal plants (Ember, January 2026).
Pumped hydro. These plants pump water uphill when power is cheap and release it through turbines when it is needed. India has 7.2 GW running (Ember, January 2026), and the national plan calls for 26.69 GW by 2031-32 (Ministry of Power reply in Parliament, July 2026). On the record night, pumped hydro and batteries supplied 4.2 GW at 10.45 pm (Grid-India).
Firm renewable supply. The Solar Energy Corporation of India (SECI) now auctions renewable power that must arrive at set times. In its February 2026 auction for 1,200 MW of assured peak supply, four hours a day, bidders offered 6,145 MW and all 1,200 MW went at ₹6.27 to ₹6.28 a unit (SECI auction result, February 2026), close to the ₹6.36 average evening exchange price MERC recorded for 2023-25.
The cost of waiting
Ember estimates India needs about 10 GWh of batteries right away just to stop wasting clean power that coal’s inflexibility pushes off the grid, which Ember’s later count puts at about 2.1 TWh for the financial year 2025-26, or 1.3% of renewable generation by its measure (Ember, June 2026). Its January estimate above (2.3 TWh) comes from an earlier report covering late May to December 2025, so the two figures are separate estimates and should not be compared or added; the June figure is Ember’s latest. Worldwide, installed battery costs fell 95% between 2010 and 2025, to about US$140 per kilowatt-hour of storage (Ember, August 2026).
Coal will carry India’s evenings for some years yet, and it does a real job when it does. How many years depends on how fast the storage already funded and tendered gets built.