Watt’s Up Doc? Does Daylight Saving Time Save Energy, or not?

One of the main reasons why Daylight Saving Time (DST) started was that it is supposed to save energy.   In reality, however, there continues to be vigorous debate over whether daylight saving time does, in fact, save energy.

The underlying reason for the adoption and maintenance of Daylight Saving Time was to conserve energy. However, there is mixed research on the subject with some studies supporting this contention and others refuting it. There was so much widespread acceptance of the premise that this time change would fuel energy conservation that daylight saving time was extended for four weeks under the Energy Policy Act of 2005. As predicted, in 2007, the US Department of Energy reported that five percent more electricity was saved daily during daylight saving time for a total of 1.3 billion kilowatt-hours, and the majority of the savings occurred in the evening hours.

Daylight saving time and energy conservation—the beginning

Daylight saving time was originally conceived to reduce energy consumption, with Germany holding the distinction as the first country to implement such as plan. During World War I, Germany adopted a daylight saving plan in order to conserve energy for war efforts. Near the end of the first world war, the US followed suit. Following the war, however, each state set its own schedule for changing the clocks.

Due to the resulting mass confusion, Congress, in 1966, established the Uniform Time Act that set the dates for “springing forward” and “falling back” for every state: the last Sunday in April and the last Sunday in October. In 2007, when daylight saving time was extended by four weeks, these dates were amended to the second Sunday in March and the first Sunday in November, which is where we are today.

Of course, Congress required some type of research to justify extending daylight saving time those four weeks.

The evidence

Enter a 2008 DOE report to Congress that examined the supposition that people should spend more time outside during “daylight” evening hours which, in turn, would decrease home electricity usage, thereby saving energy. Despite this seemingly logical assumption, researchers discovered that while brighter evenings were initially attributed to reduced energy consumption, the increasing efficiency of lights has significantly reduced the amount of energy that was the case, say, 20 years ago. In fact, air-conditioning is likely most responsible for increased energy consumption during warmer light evenings and heating during cooler dark mornings. Further, those who arise in the dark morning hours require more artificial light, thus more energy consumption. Ultimately, the data demonstrated that in the four-week extension of daylight saving time, a total of 1.24 terawatts—approximately 0.03 percent of total electricity consumption in 2007—was saved. Ultimately, because researchers only studied the beginning and end weeks of daylight saving time, they asserted that the same results couldn’t be generalized for midsummer.

Indiana Study

According to an Indiana-based 2011 study by Kotchen and Grant conducted over a seven-year period and published in Review of Economics and Statistics, electricity demand actually increased from one to four percent per year during Daylight Saving Time, costing Indianans $9 million per year in higher electricity bills. Granted, this study was done over a period of years, which which seemingly would make things better, but it didn’t take into account the general increase that every person has with power consumption over time, or the general warming that has been happening  Most things become more powerful (as an iPhone has more power now than a desktop PC used to) and thus more energy is required over years versus a single year study where that variable is not affecting results.

Which matters most?

One of the biggest problems with trying to gauge the actual energy saving during Daylight Saving Time is that policy changes are rare. The 2007 extension enabled comparison studies because there was a direct and immediate before and after against which to compare results. Otherwise, comparisons are difficult to make with many other factors almost impossible to filter out. Compounding the problem is that other oft-cited studies tend to be geographically limited—such as the Indiana—further restricting their larger applicability.

Experts assert that problems in determining whether Daylight Saving Time does save energy arise because of the inherent difficulty in studying the actual effect of Daylight Saving Time. A before-and-after comparison is necessary to determine whether any meaningful data exist, and this has only happened that one time in recent history.

Final thoughts

When all is said and done, it appears as if a little energy saving (0.03%) is probably the most logical conclusion, despite some other studies that have been published.  While that is a good thing, some energy savings coupled with lower crime, better health, safer streets and happier days without the sun setting so early in the Fall and Winter are all great reasons why one later Daylight Saving Time should be kept all year round.