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Longer Daylight Time May Save Energy — But Stats Are Stale

Wall Street Journal – November 2, 2007

In the effort to save some energy in the US, we just went through an exercise where we delayed the turning back of clocks for an additional week. We just went through the "fall back" of the "spring forward, fall back" effort this last weekend. The goal of this was to save energy as it allowed more evening light time for outside activities and kept our inside lights and TVs off.

This was probably a good thing and small steps like this are absolutely essential regardless of your beliefs on global warming. Using resources more efficiently is important as waste is almost always a bad thing. Even the most callous among us should at least live by the rule of:

"If you need it use it, if you don’t need it – don’t"

But did it work?  Did the US actually save any energy by moving Daylight Savings Time? One would think this was an easy analysis.  It is a relatively small model and is contained in only one country. But the Numbers Guy at the Wall Street Journal points out that we don’t really know.  This is concerning as we go into deliberation on laws that are designed to save us from global warming that is based on computer models.

The extra hour of primetime daylight is supposed to save energy, but the decision to make the extension was based on some questionable numbers. And any subsequent statistical support is a long way off. "The jury is still out on the potential national energy savings," says U.S. energy department spokeswoman Megan Barnett.


When Edward Markey, a Massachusetts Democrat, and Fred Upton, a Michigan Republican, introduced the bill, they said the extension could save Americans the equivalent of 100,000 barrels of oil a day — an estimate repeated frequently in the media. But that statistic relied on figures from 1974, when President Nixon sprung clocks forward early, in January, during an energy crisis.


Another supporting study, conducted in 2001 by the California Energy Commission, couldn’t compare data from the colder days of an extension — because no previous such extension had occurred. Researchers instead used a statistical model to simulate demand. Those projections showed much greater savings from trimming peak electricity demand than from cutting overall electricity usage (just a half-percentage-point drop in the latter in the winter months).


Yet another study, this one based on research from the 2000 Summer Olympics in Sydney, Australia, also raises questions about the presumption of energy savings. The games created an unintended ideal experimental situation: Daylight-saving time was extended in some regions outside Sydney but not in others.


The task is going to be difficult. California’s experience shows that such a study may be hobbled by inherent challenges. Dr. Kandel said the state’s electricity usage during the three weeks of extra daylight time this spring represented a drop of just one-fifth of one percent. That finding, however, was limited by a small sample size and the difficulty of controlling for many differences year to year, other than daylight time, that may affect energy consumption.

The plan is to assemble data from power companies’ federal filings on consumption of electricity, gasoline and other forms of energy, then to account for differences in weather, population and business activity.

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