Should I Turn Off Fluorescent Lighting When Leaving A Room?

Lighting Design Lab

Short Answer: Turn them off if you will be gone for more than about 15-20 minutes (for details keep reading).

There are a few misconceptions about fluorescent lighting that keep too many people from turning lights off to save energy. The first misconception is that it takes more energy to start a fluorescent light than it takes to run it. The second misconception is that turning a fluorescent light off and on will wear it out right away. Like many of our myths about energy, there is a small amount of truth in the belief. (Special thanks to Steve Selkowitz of Lawrence Berkeley National Labs for doing the research that this article is based on.)

Misconception #1: It takes more energy to start a fluorescent that it does to run it, so leave the lights on all the time to save money on your electric bill.

Reality: When you turn on a fluorescent light bulb (correctly called a "lamp"), there is a very brief jump in current when the ballast charges the cathodes and causes the lamp to start. This inrush of current can be many times greater than the normal operating current of the lamp. However, the spike of current draw normally lasts no longer than 1/10th of a second, and draws the equivalent of about 5 seconds of normal operation. So, if you turn your fluorescent lamp off and on more frequently than every 5 seconds, you will use more power than normal. So, normal switching of fluorescent lamps has very, very, very little effect on a power bill.

When Lamp Do Burn Out...

Even under the best lighting management practices, all fluorescent lamps eventually burn out. When they do, they need be recycled because all fluorescent lamps also contain hazardous mercury. Air Cycle recycling solutions make it simple and cost-effective. Learn more » Air Cycle lamp recycling solutions
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