Leave Lights On? No! Always Switch Lights OFF!

When I was in sixth grade, back in the early 70s, I had the worst teacher imaginable. He played favorites, and others he tortured. Guess which one I was.

I don’t remember why, but one day he went off on us. He stormed over to the light switch, and furiously turned the switch on and off, on and off, on and off, and railed at us about wasting energy.

“Every time you do this” on and off, on and off “you waste energy!” he ranted and raved.

Turns out, he was wrong, according to the following article:

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 a 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 general 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.
Environmental journalist Lori Bongiorno shares green-living tips and product reviews with Yahoo! Green’s users. Send Lori a question or suggestion for potential use in a future column. Her book, Green Greener Greenest: A Practical Guide to Making Eco-smart Choices a Part of Your Life is available on Yahoo! Shopping and Amazon.com.