Indians are cranking up air conditioning as they still work from home, while lights come back on in offices and factories with an end to COVID-19 curbs, upending power demand patterns amid a heat wave and the country's worst blackouts in years.

India has traditionally seen peak demand late in the evening when people head back home but that has shifted to mid-afternoon when temperatures are hottest, government data shows, driven by record residential daytime use, a pick up in industrial work, and more use of irrigation pumps to tap higher solar supply.

Relentless daytime demand in the world's third-biggest power market means utilities have been unable to ease output even over peak solar power supply periods, further straining grids already overwhelmed due to the heat wave baking swathes of South Asia.