Posted: 6/18/2008 1:41:05 PM EDT
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I am trying to figure out how much it costs me to run a 5000BTU window A/C unit. My electric charge is $0.067 per KWH. To convert BTU's to KWH BTU's/3413 x Efficiency% That would be 5000/3413x.75 (just totally guessing on the efficiency) = 1.099 x $0.067 = $0.074. Now assuming it is left on 24 hours a day and ignoring the compressor cycle time that would be $0.074 x 24 = $1.77/day = $53.00/month. So for a typical 110V outlet on a 15 Amp breaker you could pull 110V x 15A = 1650Watts 1650W / 1000 = 1.65KW x 24hours = 39.6KWH max from that outlet per day at a cost of $2.65/day or $79.60/month Math check isle 4!  |
Yeah, in our physics calculations anything above 50% either meant you did something wrong or someone is eligible for the Nobel Prize
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Even that wouldn't tell you the whole story. You'd need to know how long it runs and at what load. You will run the thing at significantly less than full power 24/7. |
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Nope, not quite. The A/C units are rated as BTU/hr OUTPUT. So your input is going to be higher. So, there are 12,000 BTU per "ton" of A/C. 5000 BTU then = 0.42 ton. It's roughly 1 HP per ton as a conversion ratio. Doing the conversions, you get 5000 BTU = 313 Watts. You probably have an additional 20W of overhead for such. Call it a 333Watt unit. If it runs continuously, you have 333 Watt * 24 hours/day * 30 day/month = ~240kWh. Assuming your $0.067/kWh, your monthly cost is $16/month ideally. Likely more along the lines of $25/month. |
^^this look closer to what you want. forget 'efficency'.. you're paying for watts per hour basically. |