What’s watt

SIR – VT Evenson (Letters, September 4), along with many others, doesn’t seem to understand basic physics.

Employing a two kilowatt kettle rather than a three kilowatt kettle does not use less electricity to heat a given amount of water. All it does is take a third longer, while using the same amount of electricity. In theory.

However, as has been mentioned by previous correspondents, the extra time taken increases heat-loss during heating. Therefore, more electricity is used.

Ten million 2kw kettles will not use less each than 10 million 3kw kettles. They’ll still use the same amount in total, but there will be 33 per cent more kettles switched on at any one time using the same amount of electricity as before, plus the additional heat loss.

The politicians and civil servants who issue such stupid orders as the reduction in wattage of domestic kettles mostly have degrees in humanities, and they are probably the sort of people who call in an electrician to change a light bulb. John Brandon

Tonbridge, Kent