A windy monsoon in Karnataka, India's leading state for clean energy production, last year eased pressure on the local government's three thermal coal-power plants, as humming wind turbines met power demand amid pleasant temperatures.

But to tackle this year's hot, energy-guzzling summer, with city-dwellers ramping up their use of air-conditioners and farmers their water pumps to combat heat waves and above-normal temperatures, the coal-fed plants are now running full throttle.

The south Indian state's maximum day-time temperature has been hovering three to four degrees Celsius above the 36 C to 40 C that is usual at this time of year, weather officials said.