On August 8, 2005, President George W. Bush signed the Energy Policy Act of 2005. This Act changed the time change dates for Daylight Saving Time in the U.S. Beginning in 2007. The Secretary of Energy will report the impact of this change to Congress. Congress retains the right to resume the 2005 Daylight Saving Time schedule once the Department of Energy study is complete.
So what effect does changing daylight savings have on energy use?
Energy use and the demand for electricity for lighting our homes is directly correlated to the hours we are awake. On an average day, most people go to bed in the late evening. When most people go to bed, they turn off the lights, the TV, the computer, and other electronics that use energy.
Since on average, 25 percent of a home's energy use comes from these small appliances and electronics that are used during the day, moving the clock ahead one household reduce the amount of electricity consumed each day.
Studies done in the 1970s by the U.S. Department of Transportation have shows that the entire country's electricity usage can be reduced by about one percent each day with Daylight Saving Time.
When we switch to Daylight Saving Time the sun "sets" one hour later and therefore reduces the period between sunset and bedtime by one hour. This essential trims one hour out of the day where energy is being used for lighting.
It is also assumed that less electricity is used because people are home fewer hours during the "longer" days of spring and summer. Most people plan outdoor activities in the extra daylight hours. When people are not at home, they don't turn on the appliances and lights.
So while the amounts of energy saved per household are small when they are added up the reduction in energy use can be very large.