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Grand saving


Neil Besley (Letters last week) believes that the heat from his light bulbs is just as efficient as the heat from his central heating boiler. Most electricity in the UK is generated in thermal power stations, and as a result of the second law of thermodynamics, for every unit of electricity produced, about two units of heat go up a cooling tower or into the sea.

Let's assume that for his cosy evening at home he needs five hours x 2kW of heat and the equivalent of five hours x 100W of incandescent light.

Let's also assume his boiler is 80% efficient.

Using incandescent bulbs he will consume approximately 12.5kW(heat) + 1.5kW(light) = 14kW of carbon-based fossil fuel.

Using low energy bulbs, at say 20W equivalent to a 100W incandescent bulb, his boiler output will average 2.08kW and he will use 13kW(heat) + 0.3kW(light) = 13.3kW of carbon-based fossil fuel.

Admittedly the saving is small, but there is a saving, to be added to the much greater saving (80%) when the lights only are used.

If, like me, Mr Besley used gas for his heating he would quickly see this reflected in his utility bills. A kW of heat from a light bulb costs me 10p, a kW of heat from my gas boiler costs me 3.5p. The costs of his oil will be comparable.

Thus, from self-interest alone Mr Besley could save 2p a night. Over nine months this would amount to £6, more than enough to buy the low energy bulb and dispose of it safely, in addition to the fossil fuels left for a future generation and the reduction in CO 2 emissions.

Roger C Button, rhbutton@talktalk. net

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