Here's how to calculate the cost of running an electronic device:
Unit Review:Watt [W] unit of power
KiloWatt [kW] 1000 W = 1 kW
Hour [h]
Kilowatt hour [kWh] kW times hours
Part 1) First, you need the cost per kilowatt hour. (Usually stated in cents/kWh). There are a few ways to do this. They're listed here, from easiest to most difficult:
1a) Use an estimate of about 16 ¢/kWh. This figure is an overestimate and will also overestimate your cost per month, but hey, at least it gives you a reference point.
(Skip to part 2)
1b) Another easy way is to get the ¢/kWh off a map:
http://www.npr.org/blogs/money/2011/10/27/141766341/the-price-of-electricity-in-your-state(Skip to part 2)
1c) You can also calculate this from your electric bill:
Add the off and on peak kWh
Example: 72 + 317 = 389 total kWh
Convert the the total cost on the bill to cents:
(A more accurate cost to use would be any variable costs associated with the electricity, but for simplicity lets use the total cost on the bill)
Example: $66.71 = ¢6671
Now divide:
¢6671/389kWh = 17.1 ¢/kWh
Part 2)Okay, so now that you have the ¢/kWh, you can use it for any device in your home. Here's an example using an electric heater:
Example 1:1000 Watt electric heater
12 hours/day run time
30 days/month.....on average
So now you need to know the Wh/month
1000 Watts x 12 h/day x 30day/month = 360,000 Wh/month (Watt hours per month)
Convert to kWh/month by moving the decimal over three:
Example: 360,000 Wh/month = 360 kWh/month
Now, multiple the ¢/kWh by the kWh/month:
17.1 ¢/kWh x 360 kWh/month = 6156 ¢/month = 61.56 $/month
This means to run a 1000W electric heater for 12 hours a day, for a month, at 17¢/kWh, it will cost you about $61.56 per month.
Example 2:Or, say you used the map and you live in Ohio (use map linked above):
14¢/kWhr x 360 kWh = 50.40 $/month
Example 3:Now another example, say you live in Kansas (11¢/kWh), are running a two foot, four bulb T5 HO light. Each bulb runs at 24 W and you have it on for 12 hours a day:4 x 24 W = 96 W total power consumption of light fixture
96W x 12 hours/day x 30 days/month = 34,560 Wh/month
34,560 Wh/month = 34.6 kWh/month
11¢/kWh x 34.6 kWh/month = 380.6 ¢/month
380.6 ¢/month =
3.81 $/month Happy