Center for American Progress

It’s Easy Being Green: Does Daylight Saving Time Work?

It’s Easy Being Green: Does Daylight Saving Time Work?

A look at the debate over whether daylight saving time saves energy.

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Most Americans woke up a little bit groggier this past Sunday. Thanks to daylight saving time, or DST, clocks in most parts of the United States were set one hour ahead—robbing millions of precious sleep but rewarding them with extra daylight in return.

The interval for DST has been longer in the past four years. That’s because the Energy Policy Act of 2005 mandated that DST be extended by one month. It used to last from the first Sunday in April to the last Sunday in October, but now lasts from the second Sunday in March until the first Sunday in November.

Why the switch? Or, more to the point, why have DST at all? The answer lies in the desire to conserve energy. DST proponents argue that waking up earlier to take advantage of the increased daylight reduces the need for artificial forms of lighting—and they have been making this argument for literally hundreds of years.

Ben Franklin was one of the first to propose something along the lines of DST. The Founding Father argued in a satirical piece written anonymously for the Journal of Paris that the government should tax window shutters, ration candles, and ring church bells at sunrise to encourage Parisians to wake up earlier. And, of course, Franklin wrote that firing cannons would serve as an effective alarm clock should Parisians fail to rouse.

Franklin’s tongue-in-cheek plan never caught on, predictably enough. It wasn’t until World War I that countries around the world started using DST to reduce energy consumption, beginning with Germany and its allies.

The United States passed a law in 1918 that both established time zones and instituted a DST similar to what we have now. When the war concluded the law proved unpopular enough to coax President Woodrow Wilson into vetoing its renewal.

President Franklin Delano Roosevelt later reinstated a year-round DST during World War II to curb wartime energy consumption. But that law expired at the end of the war, as well.

Finally, in 1966, a more standardized DST was implemented that coincided with the Universal Time Act. The law was adopted throughout the country in fits and starts, but the central idea was the same: reduce energy by capitalizing on the available natural light.

The logic behind DST is rather intuitive. But does it work in practice?

No clear consensus has emerged from studies despite the historical assertion that DST saves energy.

  • The Department of Transportation, or DOT, was ordered to conduct a study evaluating the time shift’s energy savings after the United States went on extended DST following the 1973 oil embargo. The DOT estimated a reduction of roughly 0.75 percent.
  • A National Bureau of Standards study two years later, however, found no evidence of a decrease in energy consumption.
  • A 1983 German study determined that energy savings could be much more than estimated in the United States. By running a simulation, the Germans determined that DST was responsible for a 1.8 percent decrease in energy consumption.
  • But another European study conducted in 1999 cut that estimate down to only half of a percentage point.

University of California at Santa Barbara professor Matthew Kotchen and grad student Laura Grant had a unique opportunity to conduct a study that would more directly test the cause and effect of DST on energy consumption. Only 15 of Indiana’s 92 counties observed DST as of 2006. The entire state adopted the new DST after the aforementioned 2005 law took effect in 2007.

Kotchen and Grant found that DST in fact increased energy consumption in the state by testing the difference in energy consumption between the two years (adjusting for variables such as temperature). The authors found that artificial light use decreased, but those savings were more than offset by the increased usage of cooling systems, which residents needed to combat the hot Indiana summers.

Whether or not DST reduces our energy usage remains unclear. The studies that have demonstrated an impact in either direction show that impact to be marginal. It is possible that DST could reduce our energy consumption, but the law alone is not enough, as the Indiana study demonstrates. We need to keep in mind the law’s intent and augment our own behavior accordingly. Realizing the potential of daylight saving time may in fact be possible by increasing awareness of ways to reduce our energy usage.

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