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Calculating the Cost of Firing an Electric Kiln
First get out your electricity bill and see what you pay per kilo-watt hour (kwh). I am on a time-of-use-meter which means that I have higher rates during peak usage, and much lower rates the rest of the time. Peak usage for me is noon to 6pm, M-F, when businesses are using a lot of air conditioning. The price difference isn’t that great in winter, but is huge in summer. So I always fire on nights and weekends. If you fire often, it might be worth a call to your power company to see if they have such an option.
Look in your kiln manual and see what the kiln wattage is. (Current models are listed on our website.) Or, if you know the voltage of the kiln (110v, 220v, etc), and the amperage (mine was 50 amps), you can multiply those numbers together to get the wattage. My Skutt 1027 (7 cubic feet) is 11520 Watts. Divide by 1000 to get kiloWatts. 11520/1000=11.52 kW Multiply that by the number of hours in a firing, and by the cost of electricity per kwh. (In my case: 11.52*8*.09) This gives $8.29. (Remember, if I fired it during a summer day it would be $30! Your price is probably somewhere in between.) This is the maximum cost of firing. It is a worst case because it assumes the kiln is running on full power the entire time, which isn’t actually the case. I cut it in half, or even more than half if doing low fire or bisque.
Now you have to add in the cost of wear and tear on your kiln. You can get scientific about this, figuring out the cost of replacement elements, etc. But I figure my kiln cost about $2000 and will last 400 firings (60% low fire/bisque, 40% mid fire.) Or about $5 a load. If I were firing cone 10 a lot, I would double that. The element life seems to decrease dramatically as you increase in temperature. But in reality my kiln isn’t worthless after that many firings, it just needs some investment in elements and bricks. So again that is a worst case.
With a few simple calculations, you can figure out what your firing costs are. I was pleasantly surprised that mine are so low. Other factors you might want to include are: time to load and unload, occasional loss in kiln shelves and posts (due to breakage or glaze melt), firing stilts, etc.