Cost of electricity in firing
Here is the formula that my husband came up with – hope it helps.
This only works well with kilns with kiln-sitters and time-limit dials… (sorry) but if you happen to have an older kiln you are using an external electronic controller with, you have a low-accuracy way to track how much electricity your kiln uses easily.
Set the time limit dial to 10 hours. Fire as usual. When finished, see how many hours are left on the dial, and subtract them from 10 to get the number of hours of time your kiln was turned on. Usually you can estimate to within a quarter of an hour.
Multiply the number of hours times the cost per KWHr, times the wattage of your kiln (In Kilo-watts, so a 3600 Watt Kiln would be 3.6 KW). For example, our smaller kiln in the store runs about 3 hours, 15 minutes (3 hours + 15/60 = 3.25 hours), and we assume 17 cents/KWHr, giving us:
3.25 * 0.17 * 3.6 = 1.989, or $2.00 per firing.
This is simplistic, of course, because we are not counting prep time, having to change elements every few years, breakage, kiln wash, fiber paper, etc. But it’s interesting that what you might assume to be the most expensive part of a kiln, namely, the power to run it, isn’t so bad after all.