Studies Cast Doubt on Value of Daylight- Saving Time

The time is adjusted on the clock atop the Clay County courthouse in Clay Center, Kan., on Nov. 6, 2010. Charlie Riedel

The state of Hawaii has never observed daylight-saving time. Arizona tried it and rejected it. Utah and Nebraska have considered dropping it. And this year, Vladimir Putin abolished the practice in Russia.

Meanwhile, one Alabama state senator likes the time change so much, he wants to stick with it year round.

Jo Craven McGinty

The historic reason for observing daylight-saving time—which ends at 2 a.m. on Sunday when clocks revert to standard time—is to conserve energy, by pushing sunlight forward into the evening, reducing the need for electric lights.

The U.S. government has found the strategy works. But two academic studies published in peer-reviewed journals rebut the idea, and one even concludes the policy increases demand for electricity.

The most recent government study, by the Department of Energy, tested whether expanding daylight-saving time by four weeks in 2007 reduced the use of electricity, as intended.

The study examined the additional weeks of daylight-saving time using data provided by 67 utilities accounting for two-thirds of U.S. electricity consumption. It compared average daily use in 2006, when there was no daylight saving, with the same period in 2007 when the extension took effect and found a reduction in electricity use of 0.5% in the spring and 0.38% in the fall.

Hendrik Wolf, an economics professor at the University of Washington whom the Department of Energy consulted, said the analysis was limited and lacked a scientific control area, making it impossible to determine whether the changes were caused by daylight-saving time or other conditions.

“We don’t know how the U.S. would have behaved without the daylight saving time extension,” Mr. Wolff said.