India’s annual growth in coal-based power generation eased in August, as renewable energy output increased to meet rising demand, according to data published on Grid-India’s website.

India’s electricity output climbed 11.6% year-on-year to 180 billion kilowatt-hours (kWh) in August, according to the data, as a prolonged heatwave and below-average rainfall boosted demand for cooling while reducing hydropower generation.

Electricity production from renewable sources, including solar, wind, and small hydropower projects, surged by 42.1% in August compared with a year earlier, reaching 35.14 billion kWh.

Coal-based power generation increased 11.3% year-on-year to 116.28 billion kWh, following gains of nearly 13% in July and about 14% in June, according to the data.

In contrast, India’s hydropower output declined 16.7% last month to 21.5 billion kWh.

Irregular monsoon rainfall also disrupted coal mining and supply operations, driving coal stockpiles at 46 power plants down to critically low levels, according to government data.

Although solar and wind power generation is rising sharply, electricity demand during non-solar peak hours remains very high, which is sustaining coal consumption, said Manoj Kumar, an analyst at the Centre for Research on Energy and Clean Air.