Author Topic: light vs air conditioner  (Read 2971 times)


  • 5 O'Clock Shadow
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light vs air conditioner
« on: May 05, 2012, 12:33:19 PM »
Is it cheaper to

-use natural light instead of lamps which increases the temperature of the house meaning more air conditioner use.
-use lamps and draw the shades. 

Theories, thoughts?

The goal would be decreasing electric bill while keeping the house at 78 or lower when its 80s outside and not feeling like you are inside a ship in space.


  • Handlebar Stache
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Re: light vs air conditioner
« Reply #1 on: May 05, 2012, 02:58:53 PM »
Wow, just think of all the factors involved.  Sun exposure of the windows in question?  Square footage of the windows?  Window coating?  Electrical use of the lamp(s) CFL? Incandescent?  Overall insulation.  Cost of electricity.  etc.

My best guess, without trying to nail down any of the above, would be to simply guess that the limited heat and electrical use of a CFL lamp would be inconsequential in the big picture if used for reading.  If you have full sun coming in a window and want to avoid the air conditioning then block that light/heat.  From there it just gets too complicated for generalization I think.


  • Stubble
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Re: light vs air conditioner
« Reply #2 on: May 05, 2012, 03:01:24 PM »
I don't use AC (unless it gets over 95* outside), but putting heavy blankets over the windows during the day, and opening the house at night really helps modulate the temperatures for me.


  • Stubble
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  • Location: New Orleans, LA
Re: light vs air conditioner
« Reply #3 on: May 06, 2012, 03:28:27 PM »
As James said, there are a ton of variables to consider on this to be truly accurate, but I suspect, given that your average window ac unit draws 1000 watts per hour, versus a 25 watt CFL that if keeping the drapes closed meant even just one hour less of cooling, it would probably be worth it. That said, you could always close the drapes just on the south facing windows and the east or west depending on time of day and that would probably give you a lot of the advantages while still bringing in some natural light.