San Francisco is turning its lights out for an hour Saturday night to increase awareness of light pollution and wasted energy.
The Christian Science Monitor said non-essential lighting will be shut off at 8 p.m.
"Our expectations in terms of actual energy savings are not as high as our expectation in terms of just communicating how easy it is to do something very simple," organizer Nathan Tyler told the newspaper.
Tyler said the Lights Out event is designed to show how individual efforts can be collectively powerful.
Los Angeles also plans to participate in the lights-out exercise Saturday night.
Copyright 2007 by United Press International
Explore further: Long-term warming likely to be significant despite recent slowdown