LONDON (Bloomberg) — Extending UK daylight saving into the winter could cut a power station's worth of electricity from peak evening demand, a National Grid Plc executive said.

About 1,300 megawatts of power demand could be slashed from peak evening usage if clocks aren't put back an hour at the end of October, Alan Smart, operations manager for National Grid, told Parliament's Energy and Climate Change Committee today. Clocks are due to go back an hour in Britain on October 31, meaning it'll get darker earlier in the evening and sunrise will come sooner.

Britain's electricity use typically has three peaks a day - - in the morning, at tea-time, or about 5 p.m., and at dark, Smart said. Changing the clocks can mean the two later peaks coincide, Smart told the committee, which is probing whether the nation could save energy by changing its time.

"If you compare Tuesday evening's demand this week, compared with Tuesday evening's demand next week, it will be higher in the order of 1,000 to 1,500 megawatts" next week, Smart said. "That's about one large power station, or in the region of 100,000 households."

The change would cut about 1,300 megawatts from peak demand in November, February and March, he said. In December and January, when it would be dark at about 5 p.m. regardless of the clocks, there's a "very marginal" effect, he said.

Even so, the change in demand is difficult to forecast because gloomy weather can affect peak times, as can television programmes, he said.