for National Geographic News
On Sunday people in the United States will roll their clocks forward an hour at 2 a.m. and begin the country's second consecutive year of extended daylight saving time.
The change, adopted into law last year, was touted as a way to save energy. But some studies suggest the move actually has consumers using more power—and paying bigger energy bills.
Hendrik Wolff, an environmental economist at the University of Washington in Seattle, is skeptical of the purported savings.
Wolff and colleague Ryan Kellogg studied Australian power-use data surrounding the 2000 Sydney Olympics, when parts of the country extended daylight saving time to accommodate the games.
The pair compared energy use in the state of Victoria, which adopted daylight saving time earlier than normal, to South Australia, which did not.
"Basically if people wake up early in the morning and go to bed earlier, they do save artificial illumination at night and reduce electricity consumption in the evening," Wolff said.
"Our study confirmed that effect. But we also found that more electricity is consumed in the morning. In the end, these two effects wash each other out."
Wolff stresses that it's difficult to determine how increased daylight saving time affected energy use across the U.S. last year. But he's inclined to reject the government's pre-change projections of modest energy savings.
Lights Out, But Bills Up
In 2007 the U.S. Congress passed a bill mandating that daylight saving time begin on the second Sunday in March and end on the first Sunday in November, creating an extra month of earlier mornings.
The U.S. Department of Energy is now sorting through the variables that drive power use—from weather patterns to the proliferation of high-definition televisions—to determine the yearlong impact of extended daylight saving time. (Related photos: sunrises and sunsets.)
Meanwhile the quirky chronology of Indiana's daylight saving time history allowed Matthew Kotchen, an economist at the University of California, Santa Barbara, to measure the time change's energy impact in that state.
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