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Durkin Tactical Franklin Armory
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Posted: 2/15/2012 2:37:28 PM EDT
I have a 3/4 horse motor (22 of them) running 24/7. I need to know the cost per-hour to run this motor. It is a 208V single phase 2-pole motor pulling about 15 RLA.

Easy math? I can pull a power bill to get the costs.

Link Posted: 2/15/2012 2:47:29 PM EDT
You have 22 3/4hp motors running 24/7

You should ask your electric company for a commercial rate if you don't already have one
Link Posted: 2/15/2012 2:50:40 PM EDT
I don't think your 3/4hp motor is pulling 15A. I think you mean LRA or inrush current. Not running current.most likely closer to two amps. @2 amps, its just over 9kw/hr x cost per kwh x 24 x 7
Link Posted: 2/16/2012 5:37:13 AM EDT
Typically, a 208v 3/4 hp motor pulls between 3.5-5 amps, depending on efficiency. 50% efficiency would pull about 5 amps, times 208v = 1.04 kwh.  22 motors = 22.9 kwh
times whatever your electric rate is (usually between 10-16 cents per kwh. Worst case, you would be paying between $2.29 - $3.66 per hour to run all 22 motors if they are only 50% efficient.
Link Posted: 2/16/2012 5:41:37 AM EDT
Most power companies have a website that will show what you pay per kwh.  You will need to know that before anyone can tell you what it costs.
Link Posted: 2/16/2012 5:57:54 AM EDT
Rocky Mountain Power charges $0.07/kwh.

I'll say a 3/4 hp motor is pulling 560 watts.  I'm lazy and just went to google to get a figure so YMMV.

Since you have 22 of them take 22 x 560 = 12,320 watts or 12.32 kw.

12.32 kw x $0.07/kwh = $0.861/hour to run all 22.

$0.861 / 22 = ~$0.04/hour to run each motor.  

$0.04 x 24 hours = $0.96.

Figure each motor costs $1 to run for a 24 hour period.

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