If you live in the USA or Canada, Daylight Savings Time 2012 ends on November 4, 2012. At 2 am, we "fall back" and gain an extra hour of sleep.
This could be a fact or a fable; depending on which study you read. One of the original goals of Daylight Saving Time (DST) was to save energy by reducing the need for lighting in the evening. Early research indicated that DST provided energy savings, but the results of more recent studies have been mixed; some even concluding that DST increases overall energy use.
A Brief HistoryThe concept of DST was adopted by the railroad industry during the 19th century as a means for standardizing their schedules. During World War I, it was introduced nationwide as an energy-saving measure. It did not become a standardized practice until the Uniform Time Act of 1966.
Energy Use and Daylight Saving TimeHow does changing the clock conserve energy? The theory is that moving the clock forward to extend daylight hours enables people to spend more time outdoors during spring and summer. With fewer hours indoors, less energy is used for lighting, watching television, or operating appliances. In the fall and winter, DST adjusts the clock back one hour, reducing the time between sunset and bedtime.
Does It Save Energy?Early research that focused primarily on lighting, found that DST did save energy. Recent studies, which incorporate more comprehensive energy-use patterns, however, have produced mixed results:
- In 1975, a U.S. Department of Transportation report found that DST might reduce the country's energy consumption by 1% in the spring.
- A 1983 study of European homes found that DST reduced lighting energy use by 4%, while increasing heating energy use 1.2%. Overall, the study concluded that DST reduced energy use by 1.8%. (Aries 2008)
- In 1999, a study of 15 European countries indicated that DST decreased lighting energy use by 1%, but increased demand for heating by 9%. (Aries 2008)
- A recent report by the National Bureau of Economic Research found that DST increases overall residential energy use by 1%. While DST reduced overall electrical consumption for lighting, these savings were offset by increases in heating and cooling demand. (Kotchen 2010)
Energy Policy Act of 2005The Energy Policy Act of 2005 extended DST three weeks in the spring and one week in the fall, beginning in March of 2007. What effect has this had on energy use? Once again, the reports are mixed. A 2007 study by the California Energy Commission concluded that the extension of DST had "little or no effect on energy consumption." (CEC 2007) A U.S. Department of Energy report, however, concluded that total energy use decreased 0.5% per day of extended DST; roughly 0.03% of total annual energy use. Energy savings occurred in the evening, with a slight increase in energy use during morning hours. Energy savings were slightly greater during the spring than in the autumn. (DOE 2008)
The Future of Daylight Saving TimeEvidence that DST saves energy is mixed and contradictory. This may be due to inconsistencies in study methods, as well as technology and lifestyle changes since its inception. Lighting systems are much more efficient, and energy-use patterns for heating and cooling systems have changed significantly. It is likely the increased use of computers and electronics have reduced the impact of DST on overall energy use as well.
In recent years, there has been debate over whether to end DST or even extend it year-round. Future research will be helpful in weighing the cost and benefits of DST and comparing it with other energy conservation methods. When it comes to public opinion, a 2010 national telephone survey by Rasmussen Reports found that many people "don't think the time change is worth the hassle."
ReferencesAries, M.B.C.; Newsham, G.R. "The Affect of Daylight Saving Time on Lighting Energy Use: A Literature Review." Energy Policy, v. 36, no. 6, June 2008, pp. 1858-1866.
California Energy Commission (CEC). The Effect of Early Daylight Savings on California Electricity Consumption: A Statistical Analysis. May 2007.
Gurevitz, Mark. Daylight Saving Time. Congressional Research Service Report RS22284. March 7, 2007.
Handwerk, Brian. "Daylight Saving Time 2012: Why and When Does It Begin?" National Geographic Daily News, March 9, 2012. (Last accessed October 11, 2012).
Kotchen, Matthew and Grant, Laura. "Does Daylight Saving Time Save Energy? Evidence From a Natural Experiment in Indiana." To be published in The Review of Economics and Statistics. February 10, 2010. (Last accessed October 11, 2012).
U.S. Department of Energy (DOE). Impact of Extended Daylight Saving Time on National Energy Consumption. Report to Congress. October 2008. (Last accessed October 11, 2012)