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When to Turn Off the Lights

11/8/2007 12:00:00 AM


Earlier this year, as I was researching an article on energy-efficient lighting, I realized there was a simple question I didn't know the answer to: When I leave the room and know I'm coming back right away, should I turn off the light?

Here's the problem: Apparently, it takes a little more energy to turn the light back on than it does to keep it running. But how long does it take before you've burned more energy by leaving the light on than it would take to turn on the bulb again?

Luckily, there's a straightforward answer. As usual with questions about home energy, the EERE had all the information I was looking for. (EERE stands for Energy Efficiency and Renewable Energy. It's a division of the U.S. Department of Energy, and their site is loaded with helpful energy saving tips.)

Here is their full, one page answer to this question. But these are the highlights:

  • To save energy, always turn off the lights when you're not using them.
  • To save money, sometimes it makes more sense to leave them on. EERE suggests leaving fluorescent lights on for up to 15 minutes if you're planning to go right back to a room. The reason is that turning these lights on and off reduces their life span, so if you switch them off more frequently, you'll have to buy new light bulbs more often.

Easy enough, right? Of course, if you really want to save energy the first big switch you should consider is from incandescent to fluorescent (or compact-fluorescent) light bulbs. The energy savings add up quickly!

Megan E. Phelps is a freelance writer based in Kansas. She enjoys reading and writing about all things related to sustainable living including homesteading skills, green building and renewable energy. You can find her on .

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