Lamps, lights, and on-off mythologies

Incandescent lights are notorious energy hogs, especially when they're left running unnecessarily. They use a lot of power to produce relatively little light, and make heat in the bargain. We should replace as many of them as we can with compact fluorescent lights (CFLs) , which use 75-80 percent less power and last up to 13 times longer (according to Westinghouse), create very little heat, and provide a warm light -- not as warm as incandescents, but better than LEDs.

We have a small house that doesn't get much direct sunlight any time of year. We run CFLs in places that are used constantly -- over the kitchen sink, over the dining room / homework / project / sit-around table, and at the bottom of the stairwell. We've found that they don't work as well in places where you need a bright light right away, for instance in the entryway, where we need to be able to see into the coat closet as we're rushing out, and don't have time to wait for a CFL to warm up. In this case we use a regular 100-watt incandescent, but only run it for 30 seconds or so.

So, is it bad to run a light for only a short period? 

Common wisdom says that you shouldn't turn incandescent lights on and off all the time, because the thermal cycling weakens their filaments prematurely. While this is inevitably true, the damage is not very significant in the context of the cost and normal lifespan of the bulb. The reduced energy cost when the bulb is off trumps the cost of any small percentage of bulb longevity lost.

What about CFLs -- do we shorten their lives by turning them an and off too often? The answer is yes, they do need to be allowed to warm up. If you turn them off and on repeatedly before they can warm up properly, they're going to expire faster than they normally would. If you won't need a CFL for more than 15-20 minutes, turn it off. If you'll be back sooner, leave it on.

Here's what looks to me like the absolutely skinny on this mythology from Lighting Design Lab.

GE Consumer and Industrial Lighting, also has a good FAQ file on compact fluorescent (CFL) technology.

What's your experience, pro and con, with CFLs versus incandescents and other types of lighting?

~ Doug Logan, New Energy Watch

Comments

[Barbara Wolfenden Owens]

This is a small thing, but ever since I replaced my little night reading light from a standard bulb type to one that has an LED, my consumption of AA batteries has plummeted. I used to have to replace the batteries approximately every three weeks; now it's once every six months, if that.

[Chris Landry]

Wow, I never knew about the benefits of CFLs. I am going to go out and buy a couple of them right now.