Up until two years ago, only 15 of
Indiana's 92 counties set their
clocks an hour ahead in the spring and an hour back in the fall. The
rest stayed on standard time all year......until the Indiana Legislature put the entire state on daylight-saving time beginning in the spring of
2006.
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 this month.
(Please see a brilliant comment on this blog below by Bill Starr)