Nature Life

When to switch off your lights

Does switching the lights on and off use more energy than leaving them on? The answer is no, despite the common misperception that turning a light on creates a power surge. The thinking is that it's more economical to just leave a light on rather than pay the costs of flicking it back on.
In reality, that "surge" lasts for only a fraction of second, according to Francis Rubinstein, a staff scientist at Lawrence Berkeley National Laboratory. Any "start-up" energy costs are minuscule at best and are more than offset by the money you save from turning your lights off, even if it's only for a short time.
So if you're strictly concerned about saving energy (and money), you should turn your lights out when you're not using them.
The bigger issue with turning lights on and off frequently, though, has to do with shortening the product's lifetime, says Christina Kielich at the Department of Energy.
It doesn't affect the lamp life of an incandescent bulb very much, says Rubinstein. So it makes sense to always turn them off when you leave room, even if it's only for a few minutes.
Compact florescent light bulbs, on the other hand, are a somewhat different story. Flicking them on and off repeatedly will affect how long they last, although, Rubinstein points out that the impact is minimal for most households.

How much flicking on and off is too much? The consensus is that it's best to turn off CFLs when you are leaving for 15 minutes or longer. In fact, Energy Star recommends installing florescent bulbs in fixtures that are used for at least 15 minutes at time. So it doesn't make sense to use them in places where you'd need to switch them on and off constantly.
The rule of thumb is a little different when you're at the office, according to Rubinstein. Turn out florescent lighting when you're leaving for at least 5 minutes. The reason? Full-size florescent systems aren't as sensitive to frequent cycling as CFLs and won't impact the life of the bulb as much.(egs/nwp)