Kiln Firing Cost Calculator (Electricity per Firing)

1. Choose how you know the energy. Estimate works it out from kiln power, hours and an average-load factor. I measured kWh lets you type the reading from a plug-in energy meter.
2. In estimate mode, pick the power source: enter the kiln's kW rating directly, or switch to volts x amps and the tool converts them with power = volts x amps / 1000.
3. Enter the firing hours for the bisque firing, the glaze firing, or both, and set the average load (the share of each hour the elements actually draw power).
4. Type your own electricity rate per kWh and the number of pieces in the load. Read the cost, the energy used and the cost per piece.

What each result tells you:

Kiln firing cost is the price of the electricity a kiln uses to complete a firing. An electric kiln turns electrical energy into heat, and your supplier bills that energy in kilowatt-hours (kWh). One kilowatt-hour is one kilowatt of power drawn for one hour.

The cost of a firing therefore depends on three things: how powerful the kiln is, how long it fires, and how much you pay for a unit of electricity. A fourth factor, the average load, matters because the heating elements do not draw full power for the whole firing. They run hard while climbing to temperature, then cycle on and off to hold it.

Knowing the cost per firing, and per piece, helps hobby potters and small studios set fair prices and decide whether to fire a full load or wait. It is closely related to costing any appliance by its power and run time, which you can explore with the appliance running cost calculator and, for makers, the 3D printer electricity cost calculator.

The whole calculation is built from one simple chain of multiplications.

The average-load factor is the only part that is not a direct measurement. A kiln rated at 7 kW does not pull 7 kW for every minute of a ten-hour firing; once it reaches temperature the elements switch off and on to hold it, so the average draw over the firing is lower. A figure around 70 percent is a common starting assumption, but it is only an example. The most reliable way to pin it down is to read actual kWh from a plug-in energy meter, which is what the measured mode is for.

Notice that the electricity rate is never built into the tool. You type your own price per kWh, so the answer is in your own currency and tariff.

Take a 7 kW kiln fired for a 10-hour glaze firing, with an assumed average load of 70 percent, and an electricity rate of 0.15 per kWh.

Meaning: at these numbers the glaze firing costs 7.35 of electricity, and if the load holds 20 pieces each one carries about 0.3675 of firing cost. Change any input and the result follows. If you also ran a 6-hour bisque firing at the same kiln and load, that adds 7 x 6 x 0.70 = 29.4 kWh, or 4.41 more, for a bisque-plus-glaze total of 11.76. The 70 percent load and the 0.15 rate here are examples only; swap in your own tariff and, ideally, a measured load.

Four inputs drive almost all of the variation in firing cost.

Kiln Power

A bigger or hotter-running kiln draws more kilowatts. If you only know the data-plate voltage and current, the tool converts them with kW = volts x amps / 1000, so a 240 V, 30 A kiln is 7.2 kW.

Firing Length

A long glaze firing with a soak at the top temperature uses more energy than a quick bisque. Count the full time the kiln is powered, including the climb and any hold.

Average Load

Elements run near full power while heating and then cycle to hold temperature, so the average draw is below the rating. A higher target cone, a cold room, or an older kiln with tired elements all push the average up. This is the input most worth measuring.

Electricity Rate

Your price per kWh has a direct, linear effect: double the rate and you double the cost. Time-of-use tariffs can make an overnight firing cheaper, which you can test with the percentage change formula.

There are two honest ways to find the energy a firing uses. Both are supported here; they answer slightly different questions.

Once you have measured a few firings, you can work backwards to your kiln's true average load and then trust the estimate mode for planning. The measured figure is the one to quote when pricing work.

Pricing Your Pottery

Fold the cost per piece into your prices alongside clay, glaze and your time, so a firing never quietly eats your margin.

Deciding When to Fire

Compare a full load against a half-full one. The firing costs almost the same either way, so the cost per piece drops sharply when the kiln is full.

Comparing Kilns or Tariffs

Test a smaller kiln, a different schedule, or an off-peak rate before you commit. Pair it with the clay shrinkage calculator when you are planning a batch end to end.

1. Using the Full Power Rating for the Whole Firing

Assuming the kiln draws its full kW every minute overstates the cost. The elements cycle off at temperature, which is what the average-load factor captures.

2. Treating an Example Rate as Fact

The rate shown here is a placeholder. Enter the price per kWh from your own bill, including any standing charges you want to account for separately.

3. Forgetting the Bisque Firing

Most work is fired twice. Cost the bisque and the glaze together to see the true cost of a finished piece.

4. Firing a Half-Empty Kiln

A nearly empty load costs almost as much to fire as a full one, so the cost per piece can balloon. Fill the kiln where you can.

5. Guessing the Load Instead of Measuring

If accuracy matters, a plug-in kWh meter removes the guesswork. Measure once and your estimates improve for good.

The arithmetic is exact, so any gap between this estimate and your bill comes from the inputs, chiefly the average-load guess, not the formula.

It depends on the kiln power, how long it fires, the average load and your electricity rate. A 7 kW kiln fired 10 hours at 70 percent average load uses 49 kWh; at 0.15 per kWh that is 7.35 for the firing.

Multiply the kiln power in kilowatts by the firing hours and by the average-load fraction. For 7 kW over 10 hours at 70 percent, that is 7 x 10 x 0.70 = 49 kWh. A plug-in meter gives the real figure.

It is the share of each hour the elements actually draw power, averaged over the firing. Elements run hard while heating, then cycle off and on to hold temperature, so the average is below the full rating.

No. The rate per kWh is always your own input, taken from your bill or tariff, so the result is in whatever currency and price you use.

Check the data plate or manual for a kW rating. If it only lists volts and amps, switch the power source and the tool uses kW = volts x amps / 1000, so 240 V x 30 A is 7.2 kW.

Enter the number of pieces in the load and the tool divides the total firing cost by that number. A 7.35 firing with 20 pieces is about 0.3675 per piece.

Yes, if you want the true cost of a finished piece. Enter hours for both and the tool reports each firing and the combined total.

Because it captures your kiln's real duty cycle, element condition and schedule, instead of a single average-load guess. Measure a few firings and your estimates improve.

Yes. A firing costs almost the same whether the kiln is full or half empty, so packing more pieces in spreads the fixed firing cost and lowers the cost each.

No. It covers the electricity for the firing only. Add any standing charge, tax, gas or labour separately when you price your work.

• Understanding kilowatt-hours and how energy use is billed (U.S. Energy Information Administration, energy and power basics).
• Electric power, current and voltage (P = V x I) (Basic Electronics Tutorials, the volts x amps relationship).
• Percentage change formula (MultiCalculators, for comparing rates or tariffs).