By EDIE LAU
November 01, 2005
After all, we'll switch on the lights at an earlier hour. When it's cold, we'll turn on the heat earlier, too.
But in California, for example, the folks at the Sacramento Municipal Utility District don't see even a blip of change in electricity demand when the time changes.
Off and on for nearly 100 years, America has observed daylight-saving time in the name of saving energy. An oft-cited federal study suggests that rolling the clocks forward by an hour from spring to fall saves the equivalent of 100,000 barrels of oil a day.
In reality, information is scarce on just how much energy is conserved by daylight-saving time.
"We don't know. We've never studied it," said Craig Stevens, a spokesman for the U.S. Department of Energy.
"There are no good data," said Ian Bartky, a scientist retired from the National Bureau of Standards.
SMUD spokeswoman Dace Udris said evening electricity use this time of year corresponds to sunset, regardless of clock time. If moving the clock backward causes any change in demand, she said, it's imperceptible.
What about the 100,000-barrels-a-day number? Setting aside the fact that America generates very little of its electricity by burning petroleum, that number came out of a report by the federal Department of Transportation 30 years ago.
Besides being dated, it's also questionable.
Bartky, who lives in Maryland, was part of a team of scientists who reviewed that study. "We found flaws in the way of calculating the energy," he said. "You correct for the flaws, and you don't see any energy savings."
Bartky said the researchers neglected to adjust for the hour that is lost or gained when the time changes. "If you compare (electricity used in) the week before with the week after, if you don't adjust for that, you see savings," he said.
More recently, the California Energy Commission studied the subject. This was in 2001, in the midst of the state electricity crisis. The commission examined whether the state could shave energy use by observing daylight-saving time year-round and/or rolling the clocks ahead by two hours, rather than one hour, in summer.
It concluded that both would save some electricity. The better bet, researchers found, was going year-round, which they calculated would cut wintertime peak electricity use by 1,100 megawatts.
Whether these findings are more reliable than the old DOT analysis is uncertain. The study was not reviewed by independent, outside scientists.
Doing a rigorous study is not a small undertaking. Bartky said there are many variables to consider, including weather and people's behavior.
For example, if there is more light in the evenings - as happens under daylight-saving time - might people drive more than they otherwise would? Also, might there be unintended consequences that outweigh energy savings?
The analysis by Bartky and his colleagues in the mid-1970s found there might be.
In response to the energy crisis of that era, Congress extended daylight-saving time in 1974 and 1975, starting it months earlier than usual.
School-safety advocates complained that the darker mornings endangered children on their way to school. Upon review, Bartky and others found that, indeed, reports of student traffic fatalities rose following the change.
Whether the increase in fatalities was real or caused by more vigilant reporting, Bartky said, the finding led Congress to cancel the wintertime extension.
This year, with energy costs rising, Congress again has tinkered with time. Under the Energy Policy Act of 2005, daylight-saving time will begin three weeks earlier and end one week later, starting in 2007.
The presumption is that the move will save energy and money, although Congress acknowledged the uncertainty by requiring the Department of Energy to report back on the effects nine months after the change kicks in.
Staff members for the congressmen who sponsored the legislation - Reps. Ed Markey, D-Mass., and Fred Upton, R-Mich. - said that even if the savings are modest, every little bit counts.
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