Becalmed in winter

sir – We have just experienced the coldest morning of the winter yet, and one message is irrefutable: we would not be able to operate without our coal-fired power stations.

With electricity demand near its peak value, these stations supplied 21 per cent of the required electricity to the grid. Wind power, though muchhyped, provided less than 3 per cent. Paul Spare

Davenham, Cheshire

sir – At present, Sizewell B nuclear power station is closed for planned maintenance, while Dungeness B and the second reactor at Heysham have been taken out of service due to leaks.

The people at National Grid must be praying for warmer weather. Paul Wood

Southampton