India curtailed 378.52 million units (GWh) of variable renewable generation in September 2026, equal to 1.28% of total renewable output, according to a report published on 16 October by JMK Research & Analytics and covered by PV Tech. Solar accounted for about 83% of the lost energy, roughly 314 GWh, while wind curtailment nearly tripled year on year to 64.98 GWh.
A seasonal dip, not a fix
Curtailment fell 43.31% from August, when 1.89% of renewable output was lost, and 24% from September 2025. The summer was far worse: between May and August 2026, curtailment ran at about four times the level of the same months a year earlier, peaking at 1,166.52 GWh in July. JMK describes the September decline as "seasonal relief rather than evidence of a structural improvement in grid integration."
The report also counts 118.6 GW of renewable capacity affected in September, 96.9 GW of it solar. JMK notes that this is a cumulative sum of daily curtailed capacity, not the capacity switched off at any single moment.
Why the power was cut
Grid-India data show two triggers. Real-time system constraints accounted for 146.73 GWh, or 39%. Emergency TRAS Down instructions, which order generators to reduce output to keep the system balanced, accounted for 231.79 GWh, or 61%, and solar made up about 82% of that. JMK says the September figures were driven mainly by the need to balance the power system "rather than by grid congestion alone".
Two states carry the burden
Gujarat and Rajasthan accounted for about 79% of the curtailed energy. Gujarat lost 187.76 GWh, or 49.6%, including about two-thirds of all wind curtailment. Rajasthan lost 110 GWh, or 29.1%, all of it solar. Karnataka and Tamil Nadu followed with 21.07 GWh and 12.93 GWh respectively.
The storage and transmission gap
JMK estimates that absorbing September's surplus would have required batteries delivering an average of 12.6 GWh a day, roughly 3 GW of four-hour storage, and recommends placing storage at Gujarat and Rajasthan grid nodes, sized to recurring surpluses. The pressure comes from rapid build-out: India added about 44.6 GW of solar in fiscal year 2026. Rating agency ICRA, cited by PV Tech, estimates the country needs about 20,000 circuit kilometres of new transmission lines and 120 GVA of substation capacity every year for five years to meet its national electricity plan targets.
What it means
India's solar bottleneck is moving from panels to the grid. For developers and investors, curtailment risk in Gujarat and Rajasthan is becoming a real revenue question, which strengthens the case for co-located storage and for power purchase agreements that spell out who bears the cost of curtailed output. For storage suppliers, a gap of about 3 GW in a single, relatively mild month points to a large and growing market. The next real test comes with the April-to-July peak generation window in 2027.
Sources: PV Tech, JMK Research.
