One of the biggest reasons we change our clocks to Daylight Saving Time (DST) is that it saves energy. Energy use and the demand for electricity for lighting our homes is directly connected to when we go to bed and when we get up. Bedtime for most of us is late evening through the year. When we go to bed, we turn off the lights and TV.

In the average home, 25 percent of all the electricity we use is for lighting and small appliances, such as TVs, VCRs and stereos. A good percentage of energy consumed by lighting and appliances occurs in the evening when families are home. By moving the clock ahead one hour, we can cut the amount of electricity we consume each day.

Studies done in the 1970s by the U.S. Department of Transportation show that we trim the entire country's electricity usage by about one percent EACH DAY with Daylight Saving Time.

Daylight Saving Time "makes" the sun "set" one hour later and therefore reduces the period between sunset and bedtime by one hour. This means that less electricity would be used for lighting and appliances late in the day.

We also use less electricity because we are home fewer hours during the "longer" days of spring and summer. Most people plan outdoor activities in the extra daylight hours. When we are not at home, we don't turn on the appliances and lights. A poll done by the U.S. Department of Transportation indicated that Americans liked Daylight Saving Time because "there is more light in the evenings / can do more in the evenings."

While the amounts of energy saved per household are small...added up they can be very large.

In the winter, the afternoon Daylight Saving Time advantage is offset by the morning's need for more lighting. In spring and fall, the advantage is less than one hour. So, Daylight Saving Time saves energy for lighting in all seasons of the year except for the four darkest months of the year (November, December, January and February) when the afternoon advantage is offset by the need for lighting because of late sunrise.

Source:
Bob Aldrich, Webmaster
(and Former Information Officer)
California Energy Commission
http://www.energy.ca.gov/daylightsaving.html