Which is most cost savings

I live in a 2 Bedroom row home. I run Central Air during the day & at night i shut it off & use a 8300 btu Air conditioner in the bedroom. Whats the best practice,what im doing or leave the central on 24/7 ?
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desgnr wrote:

Too many variables to answer definitively on the minimal information provided. Depends on how much C/A runs vis a vis the window unit, how much more is required to "catch up" the remainder of the house the next day if any, relative efficiencies of the units, etc., etc., etc., ad nauseum.
What would be most effective would possibly be to open the house at night and use attic fan and then close up the house early in the mornings. If, of course, you're in a very humid area that doesn't cool off at night, that may somewhat less effective.
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It really depends on humidity levels. High humidity really kills efficiency at the evaporator coil. It takes a lot more energy to condense water out of humid air than it does to pull heat out of hot dry air. So if you open windows on a cool but humid night, it may actually take more energy to rid the house of all that moisture the next day. It also depends on the heat loss on the South facing side of the house. If you have a lot of windows on the South wall and turn the central off during the day, you may have a HUGE heat load to get rid of when you get home.

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What you are doing now sounds best.
If you want to save some electricity, try limiting the use of the central air to only enough to dehumidiy the whole house and run the bedroom window unit enough to cool the bedroom. It's what I do.
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Yes, I agree. You're saving energy by just cooling the bedroom with the window unit at night, instead of the whole house. You can have the central AC on an automatic thermostat so it gets set to essentially be off at night and resume 90 mins or so before you get up.
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