The simple answer is that firing a kiln costs less than you’d imagine. Even though a kiln draws electricity, it does not draw it continually, so during a typical glass firing, a kiln's elements are drawing power only a fraction of the time. Most digital controllers allow you to enter your cost per kilowatt hour for electricity and they will report back the cost of the firing.
Here’s one formula for calculating the cost of firing your kiln:
1 = Amps
2 = Volts
3 = Estimated Firing time in hours time x .75 (kiln is only on full power intermittently)
4 = Cost per kilowatt hr from your electric bill
1 x 2 x 3 x 4 = Firing Cost 1,000
A longer firing will increase the energy cost, it will not be a large increase because the kiln will not be on full power any longer and the .75 factor in “3” of the formula would be lower. The formula assumes a normal, even increase per hour.
Here’s another way to calculate electric usage and costs: