How can I figure out exactly how much it will cost to run a particular electric appliance for 1 hr?

Question

I'm considering running an air conditioner

Answer 1

Yeah, but where's the rest of it?

u need the watts used from something like a kill-a-watt meter
u need the cost of electricity per kilowatt-hr

watts/1000 * hrs * cost/kwh = cost

1000 watts/1000 * 1 * $0.10/kwh = $0.10

now it it starts and stops as in compressor on/off it gets more complicated.

Answer 2

Read the wattage on the name plate. If there is no wattage listed multiply the volts by the amps to get wattage. Divide that by 1000 to to get kilowatts which is what the electric company bills you for. IF they air conditioner ran continuously for an hour that is exactly how many kilowatt hours you would be charged for. Look on your electric bill to see what the charge per kilowatt hour is and do the arithmetic.

Luckily your A/C does not run continuously so that number will be too high. You need to estimate how long it comes on and how long it stays off during a typical afternoon hot-day hour. Multiply the full time cost by that fraction of time on and that is the cost you are looking for.

You will never get "exactly" because your estimate of fraction of running time will change every hour and will change depending on how hot it is outside and whether you have the lights and the stove on inside.

Answer 3

You can read the wattage on the air conditioner but that's only peak load, an air conditioner isn't on all the time.

If you don't mind spending a little money, there's a gizmo that you plug into the wall and plug the appliance into it. It has a readout that tells you how many watts the appliance has used since you plugged it in. It's called the Kill-a-Watt.

http://www.smarthome.com/9034.html

Answer 4

The main power consuming part of the air con is the compressor but it will be turning on and off depending on how high the ambient temperature is and its rating compared to the room size. The rating plate will give you a maximum that is little use for what you are trying to do.

The only exact way is with a power meter. You can use your main house one if you are prepared to switch everything else off for that hour.