For decades, conventional wisdom has held that daylight-saving time reduces energy use. But a unique situation in Indiana provides evidence challenging that view: Springing forward may actually waste energy.
- Ben Franklin may not having been saving much candlewax by springing forward.
Indiana’s change of heart gave University of California-Santa Barbara economics professor Matthew Kotchen and Ph.D. student Laura Grant a unique way to see how the time shift affects energy use. Using more than seven million monthly meter readings from Duke Energy Corp., covering nearly all the households in southern Indiana for three years, they were able to compare energy consumption before and after counties began observing daylight-saving time. Readings from counties that had already adopted daylight-saving time provided a control group that helped them to adjust for changes in weather from one year to the next.
Their finding: Having the entire state switch to daylight-saving time each year, rather than stay on standard time, costs Indiana households an additional $8.6 million in electricity bills. They conclude that the reduced cost of lighting in afternoons during daylight-saving time is more than offset by the higher air-conditioning costs on hot afternoons and increased heating costs on cool mornings.
“I’ve never had a paper with such a clear and unambiguous finding as this,” says Mr. Kotchen, who presented the paper at a National Bureau of Economic Research conference.
A 2007 study by economists Hendrik Wolff and Ryan Kellogg of the temporary extension of daylight-saving in two Australian territories for the 2000 Summer Olympics also suggested the clock change increases energy use.
That isn’t what Benjamin Franklin would have expected. In 1784, he observed what an “immense sum! that the city of Paris might save every year, by the economy of using sunshine instead of candles.” (Mr. Franklin didn’t propose setting clocks forward, instead he satirically suggested levying a tax on window shutters, ringing church bells at sunrise and, if that didn’t work, firing cannons down the street in order to rouse Parisians out of their beds earlier.)