India's rising solar penetration is causing power grid stress: EAC-PM paper

India's rapid solar expansion is increasing grid stress as storage capacity lags, creating challenges in managing demand swings and renewable output

India’s rising solar penetration is causing power-grid stress, according to a new working paper by the Economic Advisory Council to the Prime Minister (EAC-PM).

 

The paper argued that growth in renewables, without adequate expansion in storage and without implementing other policies to smooth the net load, would add to stress in the power grid.

 

In addition to meeting more mid-day demand, solar power is forcing conventional sources, like thermal-power plants, to ramp up and down their generation more sharply to meet the net load or total load minus renewable output, the paper said.

 

“India’s demand for power is not only large, but also extremely volatile even within the duration of a single day,” the study noted, citing the example of the day India hit its all-time high peak demand.

   

On May 21 at 3:45 pm, peak demand reached 270.8 Gw but on the same day at 8:00 am, it was at 224.1 Gw.

 

In less than eight hours, the grid took on an additional load of 46.7 Gw, which is more than what the entire British grid drew at its peak in all of 2025, the paper mentioned.

 

The volatile price of electricity also draws a similar picture.

 

On the India Energy Exchange’s (IEX’s) day-ahead market (DAM), a unit of power scheduled for delivery at 1:00 pm cleared at just ₹1.56. Meanwhile, the same unit scheduled for 6:30 in the evening cleared at ₹10.00, the market’s price ceiling.

 

“Peak demand and peak price often fall at different hours of the day, and the gap between them has become an important feature of the modern Indian grid,” authors Sanjeev Sanyal and Satvik Dev note in the working paper.

 

It mentioned that there were three signals that show stress on the grid — fluctuating prices, curtailment in solar power, and power shortage.

 

About 24 Gw hours (GWh) of solar was wasted daily in May due to curtailment, which happened as a result of lack of system flexibility and transmission constraints.

 

Commenting on power shortage as an indicator of grid stress, the paper said the grid fell short of non-solar-hour peak demand on 36 days in April-May, compared with only six days for solar-hour peak demand.

 

Stress is visible in both the summer “duck” curve and winter “camel” curve, putting grid operations under stress.

 

The “duck curve” is a moniker used by grid operators worldwide for the daily net-load profile of a grid with significant solar penetration. It represents a deep mid-day trough, when solar supplies a large share of power demand, and a steep climb each evening, as the sun sets and conventional sources must rapidly ramp up.

 

The Indian grid produces a “duck” in the summer months. During the summer, demand is driven by cooling needs and solar generation runs at its strongest. This results in the net load on the conventional fleet tracing a single mid-day belly and a single evening climb, with the shape looking like a duck.

 

Similarly, the country’s grid produces a “double humped Bactrian camel” in the winter months. In winter, electricity demand spikes twice, once in the morning, when households switch on the heat and lights; and again in the early evening, when the lights and televisions come on. In between is a mid-day trough, caused by solar generation provided by the short winter day.

 

“India is not running short of electricity in the middle of the day. Instead, the stress on the grid emerges when the sun is not shining. And the stress is increasing every year,” the study noted.

 

Smoothing these fluctuations in demand and price will require adequate storage systems. However, the storage gap is large and needs to be filled quickly, it said. The paper highlights that flattening even a single summer day’s evening ramp by half requires about 130 GWh of discharge in the 1 pm-8 pm window.

 

But the country’s pumped storage and battery fleet discharged only about 23.8 GWh across an average day in May, it said.

 

Against the National Electricity Plan’s projection of 8.68 Gw of grid-scale batteries for 2026-27, only 0.27 Gw was in operation till January, even as pumped hydro very nearly reached its mark at 7.2 Gw of the 7.45 Gw projection.