Saturday, April 11, 2009
Back during the first energy crisis, when I was in the eighth grade and Richard Nixon was president, our science teacher in Southeast Junior High School -- Mr. Jagnow to the whelps -- told us that it took excess energy to turn on a light bulb and that therefore lights should be turned off only when you will not need to turn them on again right away.
Well, apparently that is an all too common misconception. With a few exceptions, you will save money and energy if you turn the lights off when you do not need them even if you expect to turn them on again a few minutes later.
Unless you feel comfortable screwing around with your electrical, the junk residential grade switches in most homes won't stand up to a lot of cycling before they fail.
Hiring someone to replace a failed switch is going to cost a lot more than any power savings.
If you've got high quality commercial grade switches, then they'll last a lifetime.
If you just look at energy cost due to the light bulb, this may be true. But as was pointed out earlier, there is a "wear and tear" cost with cycling both the switch and the buld. Cycling the system causes failures, failures cost money, and I doubt I could could figure out the correct operational time limits. This is sort of a low level example of what risk assessment is.
Seems to me Mythbusters covered this a while back. I don't remember the results, though.
However, as other people have mentioned, the wear and tear on the bulb, especially the incandescent bulb, will cause it to fail earlier than usual. A bulb can burn for a long, long time if it is never turned off. Turning a bulb off and on causes thermal stress on the filament, which leads to failure.