Daylight savings time increases energy usage

There is a natural experiment from the recent switch away from DST in Indiana.  Matthew Kotchen and Laura Grant report:

Our main finding is that–contrary to the policy’s intent–DST increases residential electricity demand. Estimates of the overall increase range from 1 to 4 percent, but we find that the effect is not constant throughout the DST period. There is some evidence of electricity savings during the spring, but the effect lessens, changes sign, and appears to cause the greatest increase in consumption near the end of the DST period in the fall. These findings are consistent with simulation results that point to a tradeoff between reducing demand for lighting and increasing demand for heating and cooling. Based on the dates of DST practice before the 2007 extensions, we estimate a cost of increased electricity bills to Indiana households of $8.6 million per year. We also estimate social costs of increased pollution emissions that range from $1.6 to $5.3 million per year.

In other words, with DST less is spent on light but more is spent on air conditioning.  Here is a summary article on the work, from today’s WSJ.  Do note this:

There may also be social benefits to daylight-saving time that weren’t covered in the research. When the extension of daylight-saving time was proposed by Mr. Markey, he cited studies that noted "less crime, fewer traffic fatalities, more recreation time and increased economic activity" with the extra sunlight in the evening.


I've heard just the opposite about traffic fatalities, mainly because people lose an hour of sleep in the spring.

First as a genuine engineer, I think we should all just operate on GMT and be done with it. The naming of time is arbitrary.

But beyond that, I've heard skeptical environmentalists argue in the past that DST would not reduce energy use, but would encourage shopping. Not sure how that works, but there's some fodder for data miners.

Brett, you obviously did not read the paper. ALL of the counties were in the southern part of the state. Take a look at Figure 1. The counties labeled NW just happened to be in the northwest corner of the group of counties at the southern end of the state. They are nowhere near Chicago.

The article also provides a nice survey or previous work on estimating the savings from DST, most of which seems inconclusive. This paper seems consistent with previous work.

Does the paper account for the huge negative of giving everyone jet lag twice a year? Or the semiannual confusion and lost productivity from getting up too late or too early?

given that in the summer there will be extra demand for cooling and in the fall for heating, how much of this is attributable to daylight saving time?

did they compare regions with similar climates and economies but with and without dst's? this would make it more believable to me


By and large, the school year is conducted in the time when DST is NOT in effect, thus the whole "kids waiting for the bus in the dark" argument is a moot point. As a native Hoosier, I remember waiting for the bus in the dark or pre-dawn for 75% of the school year.

They can take my extra hour of sunlight in the evening during the summer when they pry it from my cold, dead hands.
Indiana is a terrible example, because it is so far on the western side of the Eastern Time Zone, that they get plenty of light as it is during the evenings. For states on the eastern edge of the time zone, getting rid of daylight savings time just makes it light intolerably early in the summer, and prevents me from getting in a full 18 after work.

Another example of social engineering gone wrong. The government should get out of the "time travel" business and let people decide when and where they will go to work, etc. That may put a little less food on the tables of researchers, but it would relieve so much wasteful spillovers (just from switching...) as to be worth it. Nature went for millennia without clocks, and it's bad enough that we use them, but let's not abuse them!

What's wrong with the government doing it if there are tangible benefits?

If there are tangible benefits. That's the question here -- it seems that there is no good evidence of tangible benefits. It's an example of "faith based" policy-making--which unfortunately seems to be the norm for all types of government policies, ranging from drug prohibition to nation-building: somebody speculates that a policy should have a particular outcome, and the politicians treat it as revealed truth.

On the big picture, I agree that elected officials could play a role in coordinating seasonal changes to our schedules, but might it be more reasonable for them to simply declare "if you want to switch to a summer schedule (starting the day earlier), we suggest that everyone do it on March 4" -- and leave the clocks alone.

Not having read the paper, I wonder whether these results are replicable in places where air conditioning is uncommon (i.e., the vast majority of the world, including Western Europe). Probably not.

Farmers. How quaint. Didn't we outsource all of those, too?

The engineer, the happy juggler, the NASCAR wife all just hint at the madness of DST. It is not that early light costs us more or that evening light costs us more, the changing clocks cost us either way.

For all of the people who claim to benefit from DST, for all of the studies that claim the "extra" time is better used in the morning, there seem to be just as many people who claim DST is bad, studies that claim that light time is better used in the evening.

It is ridiculous. Have been saying it for years.

I'm probably more libertarian than anyone here, but I don't see a problem with daylight savings time. After all, the government doesn't force anyone to set back their clocks. There is no law against ignoring daylight savings time, or changing your schedule around it that I know of (and if there is, would it ever really be enforced?).

Businesses will obviously do whatever they think is in their best interest, proclamations of "daylight" notwithstanding. Its easy to alter work hours twice during the year with or without government reminding us (easier, I would argue, than setting every damn clock back and building DST functionality into modern clocks).

I have always noticed that my garden starts to improve around the time we go on daylight savings time. The plants really thrive with that extra hour of sunlight.

Without rewriting a paper that I've already written, a few of the finer points: (1) All the results take into account weather (over 10 million data points from 60 NOAA weather stations) and solar data (daily sunrise/sunset for each zipcode) for the exact location and electricity billing period, therefore these variables are "controlled for" and the data still show a marked difference in DST months. (2) We were able to test if the places used different amounts of electricity during non-daylight saving time months and they didn't -- this is like a falsification test of our method. (3) The change is from both AC in the summer and heating in the cooler months and weeks of DST extension. These are "average" behavioral changes over the whole of the population in Southern Indiana, about a quarter million people, and verified by an energy simulation model. (4) and John S -- funny ;) See, too. (5) Thanks for the posts!

'Enacting a law that might do a little bit of good is a bad idea if only because it encourages all kinds of other "little bit improvement" laws that seriously infringe on liberty'

How does DST infringe on liberty? It seems like you're a libertarian paranoid; sorry I could not find a more polite way to express this thought.

Also, you left out the emphasis on might in my quote. It changes the meaning of the sentence, similar to saying "might or might not, the evidence isn't clear".

Market discovery is a much better way of figuring out what works as a general rule than headline hungry politicians picking and choosing for us. I realize this doesn't have much of an effect regarding DST, but again, it is all about habit of thought and action.

A little historical note for those who favour no government intervention in clock times.

There were no standard times. And then the railway was invented. Bristol on the West Coast of England had clocks running 15 minutes later than London. This made the London to Bristol train timetable impossible-- each town had a different clock setting.

And so, Parliament legislated Greenwich Mean Time, and that the whole country had to follow it. The inconvenience to those West of London be damned.

Government is already in the time business. And the weights and measures business. In fact, it invented them (by standardising the anarchy that was already there).

The main argument for DST, at least here, is fewer child deaths. I wasn't aware of any real argument about energy usage (although I believe we did have British Summer Time +1 ie GMT +2 during WWII).

The reason being that drivers are more alert in the morning, and therefore more able to drive in the dark.

Since children typically go home around 3.30-4.30pm in the UK (London is at 50 degrees latitude) it's dark in winter, or twilight. The moment of peak auto accidents.

So if we stayed on European time (GMT + 1) all year round the estimate is we would save a certain number of children from being run down or suffering serious injury.

However Scottish political constituencies (north of 54 degrees N) in particular would find this unacceptable: farmers have to work for too long in the dark.

Another way to put this is that the "slippery slope" argument is bunk.

Eric H

Government invented standard time. There wasn't a national standard of time before government legislated it.

Before that, individual communities set their own times. However with the arrival of the railway, and travel that was faster than a day to get anywhere, that became impossible: railway timetables.

So government is already inextricably linked to the problem of time-setting.

If government didn't intervene, you might find half of the population used Daylight Savings Time, and half did not. Leading to very large transactional costs due to errors and the need to communicate, at all times, which time we were talking about.

None of us would know what the correct time was, in any case. Because we would all have different clocks.

'standard liberal prescription for decades'.

How about 'standard prescription for the role of governments since the 19th century'? To set standards for time.

What the WSJ failed to mention is that the finding was for residential energy consumption only. If you factored in use for commercial and government purposes, the finding might be reversed!

The majority of heating in Indiana is NOT from electricity (according to Duke Energy). Seems to me that they should have done their homework when concocting the heating-cooling argument.

I've ignored DST for years. I have a sign on my business door letting customers know that I'm still on standard time. There has been no change in my business. I open my door at 8am and close it at 4:30 pm year round. Most customers think it's a good idea.

If I want to have extra time at the end of the day then I take off work an hour early.

One more point. Have you ever tried to set a sundial to daylight savings?

Personally i think that the guy who thought up DST ought to be shot. Why dont they just change your work hours instead?

Oh, did i mention i live in Arizona? lol

Daylight savings time wastes energy, wreaks havoc amongst body rhythms and does nothing but cause problems with production for dairy farmers. Just as the mornings get to the point where the kids can wait for their school buses in daylight, they change the time so they are, once again, waiting for buses in the dark. Living in Texas, starting the day earlier still does nothing in conserving energy. We use more energy lighting up everything, and it still gets hot enough, early enough, for the cooling of our schools & businesses for customer/student use a moot point. They should do away with DST all together. A few years ago, one senator proposed to do just that, he was laughed off the floor by the other delegates.

"...and does nothing but cause problems with production for dairy farmers..."
Huh? I didn't realise cows cared about the time.

"They should do away with DST all together" - this may solve some of your objections to it. How about going the other way, and choosing a timezone that suits the region, rather than some arbitrary choice made many years ago?

Cows get used to being milked at the same time of the day, thus, there are certain times of the day they produce more milk. When DST is enacted, dairy farmers must milk the cows earlier than their usual time in order to get the milk ready for market, thus, reduced production until the cows adapt to the change.
There are states that have done away with DST and I have yet to hear any complaints from the people living there about it.

It is an useful of methods

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