Replace Incandescent Bulbs to Save on Air Conditioning

by Erik North on April 17, 2012

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We’re in the midst of the first paradigm shift in electric lighting since … well, since forever. It’s been over 200 years since incandescent lights were first conceived and over 130 years since Joseph Swan and Edison nailed the particulars. In the intervening more than a century? Nothing much has changed in the lighting front.

Incandescent Bulbs Are How Hot?!?

Very very hot. One thing we’ve grown accustomed to is how hot incandescent light bulbs are. Standard bulbs are actually pretty good heaters.

Well, if you live in a cooling climate (a hot climate like the American South where the air conditioning is used predominantly) incandescent bulbs cost you money and energy in two ways. They can be replaced with more efficient CFLs, LEDs, or ESL bulbs and they’re causing your air conditioner to work too hard.

These replacement bulbs put out much less heat and consume much less electricity.

Heat and Incandescent Bulbs

Incandescent bulbs produce light by heating a tungsten filament until it glows white hot. Over 90% of the electricity running into the bulb radiates out as heat with the filament reaching over 3000 F. Isn’t that just an insane, crazy temperature?

A Tiny Bit of Math

Suppose you have a 100 watt light bulb. 1 Kilowatt/hour equals 3412 BTUs. Over 1 hour, that 100 watt bulb will put out well over 300 BTUs of heat. If you have a wall mounted air conditioner rated for 6000 BTUs running in the same room, having that light on is exactly like having a small heater on while trying to cool.

There is resistance among some folks in the move away from incandescent bulbs. CFL bulbs (and LED and ESL) use much less electricity than incandescents. But they also put out far less heat than incandescents. If you live in a hot climate where air conditioning use is common, this is another money saving reason to make the switch away from incandescent bulbs.

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