Matthew Kotchen is a professor of economics at Yale University and recently served as the deputy assistant secretary for environment and energy at the U.S. Department of the Treasury.
March 6, 2014
If you ask someone why we have daylight saving time, the most likely answer you’ll hear is that we change the clocks to help farmers. But daylight saving time has nothing to do with agriculture, except that farmers have historically opposed it, preferring morning sunlight to darkness when, say, milking the cows.
The annual time changes are about energy conservation. That is why daylight saving time exists in the United States and dozens of other countries, affecting more than 1.6 billion people worldwide. The argument, dating back to Benjamin Franklin and others before him, is that changing the clocks — with a spring forward and fall back — will decrease energy consumption because more sunlight in the evenings will reduce the need for artificial illumination.
But does this actually save energy? Recent studies suggest it has the opposite effect. One study that I worked on took place in Indiana, where daylight saving time was first instituted statewide in 2006. We found that the time change increased residential electricity consumption by 1 percent over all, with monthly increases as high as 4 percent in the late summer and early fall. The consequence for Indiana has been higher electricity bills and more pollution from power plants.
The reason is that daylight saving time reduces demand for residential lighting, yet increases demand for heating and especially cooling. So, while Benjamin Franklin’s argument still applies to lighting, the more important effect today comes from air conditioners. And in regions where demand for air conditioning is greater and growing, daylight saving time is likely to increase electricity use even more. Arizona, one of the hottest states, may have it right by not changing the clocks.
Of course, many people favor daylight saving time for reasons unrelated to energy, one of which is more time in the evenings for outdoor leisure. But many others find the switch disruptive and would prefer the early morning sunlight. One unifying theme I have found since conducting research on daylight saving time is that virtually no one has a neutral opinion on the subject.
As the debate continues this year, readers and policy makers should keep in mind that despite its intended effect, a growing body of evidence reveals that daylight saving time increases rather than decreases energy consumption. There are certainly benefits, but energy savings is not one of them – a tradeoff to acknowledge as we enjoy an extra hour of sunlight on those long summer evenings.