NPR logo

Study Tracks 'Daylight Saving' Energy Use

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript
Study Tracks 'Daylight Saving' Energy Use

Research News

Study Tracks 'Daylight Saving' Energy Use

Study Tracks 'Daylight Saving' Energy Use

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

A study conducted in Indiana concluded that Daylight Saving Time uses more energy than it conserves. Matthew Kotchen, an economics professor who worked on the study, talks with Melissa Block about what researchers learned.


This weekend we'll lose an hour of sleep but gain an hour of daylight as Daylight Saving Time kicks in, at least in most of the country. But Matthew Kotchen is here to tell us if we think we're saving energy on Daylight Saving Time, we should think again. Matthew Kotchen teaches economics at the University of California, Santa Barbara.

And is that the assumption, Mr. Kotchen, that springing forward means we use less energy?

Professor MATTHEW KOTCHEN (Economics, University of California, Santa Barbara): Yeah, it is the assumption that has carried through our energy policy here in the United States and in fact the original rationale was first put forth by Benjamin Franklin a long time ago and has carried through to World War I, World War II.

BLOCK: You ended up doing a study in Indiana measuring energy consumption there. What did you find?

Prof. KOTCHEN: Well, we focused on Indiana because the unique history of the practice of Daylight Saving Time there and it turns out that for the several decades, many counties were not practicing Daylight Saving Time but some of them were. So this created what a social scientist call a natural experiment in order to estimate the effect of Daylight Saving Time on energy consumption. And the reason why this arose was because the whole state changed to uniform application of the policy beginning in 2006.

And so we collected data on 250,000 households and seven million observations of monthly billing data, and we estimated that contrary to the conventional wisdom Daylight Saving Time actually increases electricity consumption rather than decreases it, and our estimates range between one and 4 percent.

BLOCK: And how much would that be in dollars, say, per household?

Prof. KOTCHEN: Based on very conservative estimates on the price of electricity that people pay in southern Indiana, it costs the average household $3.18 per year, which may not sound very much on a house-by-house basis, but if you aggregated up to the population of Indiana, it turns out to be $8.6 million per year. And that's only the state of Indiana.

BLOCK: And what's the reason for that increase in energy use then?

Prof. KOTCHEN: What we found is that that Benjamin Franklin effect is in fact alive and well, but while Benjamin Franklin could foresee many things, he didn't necessarily foresee the prevalence of heating and cooling that we have today. And so there's a heating and cooling effect that runs in the opposite direction of the lighting effect. And what we're finding is that that affect, an imbalance, results in an increasing consumption rather than a decrease.

BLOCK: So that would mean what - we're turning on if it's cold, we're turning on the heat earlier and by contrast, we're using more air conditioning later in the day?

Prof. KOTCHEN: That's exactly right. And so if you are a household, say, that never changes your thermostat throughout the day, then Daylight Saving Time would obviously have no effect on your electricity demand and you might in fact get the savings from the lighting. But if you're a household that turns the heat down when you go to bed, when you wake up in the early spring, in the late fall, Daylight Saving Time is causing you to wake up at the coldest, darkest part of the day. And if you turn up your heat, you probably have to run your heat harder than you otherwise would have.

At the same time, in the middle of the summer, you've taken hour of sunlight from the early morning when you might have been sleeping and put it to the evening. And if that's the time when you really want your house to be cool in the evening, say, when you're having dinner, you probably are going to be running your air conditioning stronger and that explains the effect that we're finding.

BLOCK: And again, nothing that Ben Franklin would have factored in necessarily?

Prof. KOTCHEN: Well, Benjamin Franklin wouldn't have factored that in, although if I happen to be sitting next to Benjamin Franklin as he was taking about saving all the towel(ph) and wax from not having to burn candles in the evening, I would have pointed out that he's probably using coal in order to heat the dwelling that he was in while he was doing it, and if he really wanted to consider the effect on energy, he should probably account for that as well.

BLOCK: Hmm. Now, you're an economist, not a sociologist, so this may be unfair, but I would bet you would agree with me that there are huge social benefits to Daylight Saving Time. If you have people out and about late in the day, sitting on their porches, seeing their neighbors, that's something taht maybe you can't measure at all.

Prof. KOTCHEN: Yeah, even as an economist, I recognize the social benefits as well and in fact, we talk about this quite a bit in our research and in our paper. But what we hope to come out of this study is at least, well, if we're going to pursue Daylight Saving Time, then we should at least think about the fact that there may be an energy cost associated with it.

BLOCK: Okay, Matthew Kotchen, thanks so much.

Prof. KOTCHEN: Thank you.

BLOCK: Matthew Kotchen of the University of California, Santa Barbara.

Whether it saves energy or not, Daylight Saving Time kicks in this Sunday at 2:00 a.m.

Copyright © 2008 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.