Dilemma: Guiding Light

Q: My mom used to say that if I’m going to leave a room for just a few minutes, I should leave the lights on because it takes more energy to turn lights off and on in a short period of time than it does to just leave them on. Is that true?

A: Though there is a surge of energy for a fraction of a second when you turn on a light, it is such an insignificant amount that it is not even measurable on a normal meter, says Steve Selkowitz, a lighting expert at the Lawrence Berkeley National Laboratory. So whether you’re leaving for a few hours or just stepping out for a few minutes to grab the mail, Selkowitz says the most energy-efficient strategy is to always shut the lights off.

Issue 25

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