Kiln Firing Cost Calculator

A kiln firing cost calculator estimates the electricity cost of one firing as kiln power (kW) × firing hours × duty cycle × your price per kWh. Enter your kiln’s nameplate wattage (or its volts and amps), the firing length, the share of time the elements are on, your rate and, optionally, the pieces in the load.

How to use the kiln firing cost calculator

1. Choose how you know the power. If your kiln’s data plate or manual lists watts, pick “Watts from data plate.” This is the preferred option. If it lists only volts and amps and the kiln is single-phase, pick “Volts × amps” for an approximation.
2. Enter the kiln power. Type the wattage, or the voltage and current.
3. Enter the firing time. Count from when the kiln switches on to when it shuts off. Your controller’s firing log or schedule shows this.
4. Enter a duty cycle from 1% to 100%. This is the percentage of the firing during which the elements actually draw power. Leave it at 100% to see the maximum possible cost, or enter your own estimate.
5. Enter your electricity rate per kWh from your utility bill. Results are in whatever currency you enter the rate in; the $ symbol is shown for display only.
6. Optionally add pieces per load (a whole number from 1 to 10,000) to see the cost per piece, and firings per month to see a monthly total. Then press Calculate.

The result shows the cost per firing and, if you entered pieces, the cost per piece beside it. The per-piece figure is electricity only. It does not include clay, glaze, kiln wear or your time. You also see the energy used in kWh, the maximum cost at 100% duty, the average cost per hour, the energy in megajoules, and a summary of your assumptions with the formula filled in using your numbers. The headline firing cost is rounded to cents, while the filled-in formula shows the unrounded firing cost, which is the value divided by the number of pieces. Very small values appear in exponent form (for example 1 × 10^-9) so a positive cost is never shown as zero, and “≈” marks a rounded result.

The formula behind kiln electricity cost

A kilowatt-hour is the energy delivered by one kilowatt of power for one hour, so energy is power multiplied by time. Electric kilns are rated in watts, and 1 kW = 1,000 W. When only volts and amps are given, P = V × I gives an approximation of the power for a single-phase resistive load such as kiln elements. For example, 240 V × 30 A ≈ 7,200 W. Prefer the nameplate wattage when you have it.

A kiln’s controller switches the elements on and off to follow the firing schedule, so the elements are not on for the entire firing. The duty cycle accounts for this:

• kW = watts ÷ 1,000
• Energy (kWh) = kW × hours × duty cycle % ÷ 100
• Cost per firing = kWh × rate per kWh
• Cost per piece (electricity only) = unrounded cost per firing ÷ pieces per load
• Energy (MJ) = kWh × 3.6

Worked example: a 9,600 W kiln fires for 10 hours at a 70% duty cycle, the example rate is 0.15 per kWh, and the load holds 40 pieces. The power is 9,600 ÷ 1,000 = 9.6 kW. The energy is 9.6 × 10 × 70 ÷ 100 = 67.2 kWh. The cost per firing is 67.2 × 0.15 = 10.08, in the same currency as the rate. The electricity cost per piece is 10.08 ÷ 40 = 0.252, which rounds to 0.25.

The table below works through the formula for a few illustrative inputs. The duty cycles, rates and piece counts are example inputs, not typical values, and costs are in the same currency as the rate. Cost per piece is always divided from the unrounded firing cost (for example 1.242, not the rounded 1.24). It is shown with two decimals from 0.10 up and three decimals from 0.001 to below 0.10. A positive cost per piece below 0.001 would round to 0.000, so the calculator shows it as “less than 0.001” instead. Likewise, a firing cost below half a cent is shown as “less than 0.01” rather than 0.00.

Finding your kiln’s wattage and other inputs

The most reliable input is the wattage on your kiln’s electrical data plate or in the manufacturer’s specification table. The same model can have a different wattage depending on supply voltage and phase. The examples below come from published manufacturer tables and are for reference only. Always use the figures for your own kiln.

For single-phase kilns, the published watts approximately match volts × amps, allowing for rounded ratings. For example, 240 × 48 = 11,520 W for the Skutt KM-1022, and 240 × 26.7 ≈ 6,408 W against the KM-818’s listed 6,400 W. For a three-phase kiln, volts × amps does not give the wattage, so enter the nameplate wattage directly.

Duty cycle depends on your kiln, the load, the firing schedule and element condition, so this page does not suggest a “typical” figure. Calculate at 100% to see the most a firing could cost. To calibrate the figure, measure the kWh for one firing with a dedicated meter or your utility’s usage data, then use this formula: duty cycle (%) = measured firing kWh ÷ calculated 100%-duty kWh × 100. For example, an 11,520 W kiln firing for 8 hours gives 92.16 kWh at 100% duty. If it actually used 46.08 kWh, the duty cycle is 46.08 ÷ 92.16 × 100 = 50%. Use that value for future estimates with similar loads and schedules.

For the rate, use the per-kWh figure on your bill. If you have time-of-use pricing, use the rate for the hours when your kiln fires. For pieces per load, count the items in the firing. The resulting per-piece figure is electricity only, and this estimate does not include fixed monthly charges, fees or taxes.

Methodology & sources

The calculator uses only basic, published physics and unit conversions. Every kiln-specific value comes from you. It does not assume a typical duty cycle, firing time, electricity rate or load size. Cost per piece is calculated from the unrounded firing cost, and the filled-in formula shows that unrounded value; per-piece values below 0.001 are shown as “less than 0.001” rather than rounded to zero. Results are in whatever currency you enter the rate in; the $ symbol is shown for display only.

• Wikipedia — Kilowatt-hour: 1 kWh is one kilowatt for one hour and equals 3.6 MJ.
• Wikipedia — Electric power: P = V × I, used here only as a single-phase resistive-load approximation.
• Skutt KM-614, KM-818, KM-822 and KM-1022 specification tables: example volts, amps and watts.
• L&L e18T-3 and L&L e23T-3 product pages: example wattage by voltage and phase.

Last updated: November 2026

FAQ

How do I calculate the cost of a kiln firing?

Multiply the kiln’s power in kilowatts by the firing hours to get the maximum kWh. Scale that by the share of time the elements are actually on (the duty cycle), then multiply by your electricity rate per kWh. Divide by the number of pieces in the load for an electricity-only cost per piece.

Where do I find my kiln’s wattage?

It is printed on the kiln’s electrical data plate and in the manufacturer’s specification table, and that nameplate wattage is the best figure to use. If a single-phase kiln lists only volts and amps, volts × amps gives an approximation for a resistive load like kiln elements.

What duty cycle should I enter?

Duty cycle is the percentage of the firing time during which the elements draw power; it is your own estimate, and 100% gives the maximum cost. To calibrate it, use duty cycle (%) = measured firing kWh ÷ calculated 100%-duty kWh × 100. For example, 46.08 ÷ 92.16 × 100 = 50%.

Can I use volts × amps for a three-phase kiln?

No. Volts × amps is only an approximation for single-phase resistive loads. For a three-phase kiln, use the wattage stated on the data plate or in the manufacturer’s specifications.

Where do I find my electricity rate?

Your utility bill shows the price per kWh. If your plan has tiers or time-of-use pricing, use the rate that applies when you fire.

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