Power generation in the country expanded by over six per cent last month even as 25 thermal power stations battled with a coal stock of less than four days. As per Central Electricity Authority data, power generation in March increased 6.39 per cent at 2,550 million units as against the programmed 2,397 million units. On the other hand, the fuel stock position at the thermal power stations was abysmal with less than four days of reserves at 25 plants and less than seven days stock at 30 power stations, the data showed.