Having moved the clocks forward for Daylight Saving Time (DST), I thought it would be interesting to revisit the energy impact of DST.  I expected to find a plethora of data extolling the virtues of DST.  Instead I found a mish-mash of data and opinions.

DST was first adopted in the United States during World Wars I and II, but it wasn’t until the energy crisis days of the 1970s before it was widely adopted across the country.  A 1975 study by the U.S. Department of Transportation investigated the energy impact of DST and found that it reduced the country’s energy use by 1% each day.  A more recent 2008 U.S. Department of Energy (DOE) study found that extending DST to the second Sunday in March through the first Sunday in November reduced electricity use by 0.5% each day during the added DST weeks.

I also found some state-specific studies, most notably this 2007 California Energy Commission study that found starting DST early in California had no significant energy impact and this 2006 National Bureau of Economic Research study from Indiana that found DST actually increased energy use for Indiana residents by 1% to 4%.

Looking at other countries’ research produces even more conflicting information on the subject.  With so much contradictory information, isn’t it time we re-evaluated this practice as a country?

Wake Up

It’s questionable to use a 40-year old study as the validation for any practice.  Energy-use profiles have certainly changed from the 1970s to today.  One of the biggest changes is the increased use of air-conditioning across the country.  Sure enough, the 2008 DOE study said that Southern states saw the least impact from the DST extension, likely due to air-conditioning.  Undoubtedly, other factors like increased appliance penetration and plug loads have changed how we use energy compared to 40 years ago.

By no means am I saying we should abandon DST.  However, as DST also comes with a lot of headaches (and at least one night of interrupted sleep), we should really have a better grasp of why we’re doing it.  It’s been over 40 years since we had a thorough, nationwide study on the impact of DST.  For a country whose government is going through a budget crisis, we owe it to ourselves to know if a practice first started in 1918 is still delivering value.