By Andrea Lang, Energy Fellow
Last Sunday, Americans (save Hawaiians and most Arizonans) lost an hour of their weekend to daylight saving time. While many Americans have a vague understanding that daylight savings time is meant to save energy, others mistakenly believe that the policy was designed to help farmers (in fact, most farmers have been opposed to daylight savings time from the beginning). Today’s blog dives into the history and justification for daylight savings time, and examines the studies into its efficacy in terms of energy conservation.
Who thought daylight saving time up?
Many attribute the idea of daylight savings time to Benjamin Franklin’s 1784 essay in the Journal of Paris. Mr. Franklin wrote in that essay about the expense of candles used in the dark hours of the evening and the wasted daylight hours spent sleeping in the morning. He jokingly suggested that “[e]very morning, as soon as the sun rises, let all the bells in every church be set ringing; and if that is not sufficient?, let cannon be fired in every street, to wake the sluggards effectually, and make them open their eyes to see their true interest.”
We can all be thankful that Benjamin Franklin’s solution of firing off cannons at sunrise every morning was never adopted. Instead, a New Zealand entomologist seeking more daylight hours by which to examine insects first proposed the idea of adjusting the time, resulting in the first daylight savings time in 1917 New Zealand. Until the US permanently adopted a daylight savings time in the mid 1960s, it was purely a wartime policy. During World War I, Congress passed the first daylight savings law in 1918, but repealed it just a year later in 1919. Another daylight savings time law during World War II lasted from 1942-1945. It wasn’t until 1966 that Congress established a permanent daylight savings schedule for the purpose of conserving energy. That schedule has been periodically changed to shift or expand daylight savings time. The existing schedule was established by the Energy Policy Act of 2005, which extended daylight savings time by several weeks.
Does it make sense?
I was able to find two recent American studies on the electricity savings afforded by daylight savings time, both conducted in 2008. Each comes to a conflicting conclusion:
The first study is a Department of Energy (DOE) report to Congress that was required by the Energy Policy Act of 2005. The DOE study simply compared annual electricity consumption between different years, using the difference between the electricity used in the added weeks of daylight savings and the electricity used before the 2005 act extended daylight savings. It concluded that the total electricity savings amounted to 1.3 Terawatt-hours, amounting 0.5% per day in electricity savings.
On the other hand, a different independent 2008 study found that daylight savings time actually increases electricity demand by 1%, at least in Indiana. That study used data from Indiana, where various counties had historically practicing daylight savings time, while others had not. When a 2006 state law required all counties to begin practicing daylight savings time, the researchers took advantage of the unique circumstances that created a set of treatment and control data sets. The ability to use a control set of data makes this study more appealing than the DOE study, because it allowed the researchers to say more definitively whether energy savings or losses were a result of the policy itself. The study concluded that although Benjamin Franklin was correct that daylight savings time saves on electricity used for lighting, those savings are more than offset by an increase in consumption used for heating and cooling.
Both studies have their limitations. As I’ve noted, the DOE study is simplistic and lacks a control data set to confirm the cause of the alleged 0.5%/day savings. The Indiana study, while well designed, is specific to Indiana, which experiences more seasonal variation than many other states. More temperate states may use less energy for heating and cooling. Regardless, given the conflicting results of the two 2008 studies, it’s surprising to me that more haven’t been conducted.
Perhaps I’m just grumpy about my lost hour of sleep on Sunday, but the justification for daylight savings time seems dubious at best. While energy conservation is an important goal, it may be past time to reevaluate whether daylight savings is the best policy to that end.