Every studio knows roughly what the electric bill is and nobody knows what a single mug costs to fire. It is two multiplications and a division, and once you have it, member pricing and firing fees stop being guesses. A glaze firing usually costs more per piece than a bisque, and the reason is entirely visible in the numbers.
An 8.5 kW kiln on an 11-hour glaze firing at $0.14/kWh costs $13.09 — 36 cents a piece across a 36-piece load.
The example
Three firings from one week, on the same meter and the same rate.
| A | B | C | D | E | F | G | |
|---|---|---|---|---|---|---|---|
| 1 | Firing | Kiln kW | Hours | $/kWh | Pieces | Firing cost | Cost per piece |
| 2 | Bisque cone 04 | 8.5 | 9 | 0.14 | 48 | $10.71 | $0.22 |
| 3 | Glaze cone 6 | 8.5 | 11 | 0.14 | 36 | $13.09 | $0.36 |
| 4 | Test kiln | 1.8 | 6 | 0.14 | 10 | $1.51 | $0.15 |
The formula
The intermediate kilowatt-hour figure is worth knowing even if it does not get its own column:
How it works
Four inputs, and the last two matter most:
B2*C2is kilowatt-hours. Read kilowatts off the kiln's data plate — a common studio electric kiln is 8–11 kW, a test kiln 1–2 kW.*D2applies the rate. Use the all-in figure from the bill including delivery and demand charges, not the headline supply rate; the difference is often a third of the cost./E2is the part that changes behaviour. A half-full kiln costs almost exactly what a full one costs, so pieces-per-load is the lever, not hours.- Round to cents. Fractions of a cent per mug are noise, and a studio fee schedule quoted to four decimals looks like it was never sanity-checked.
This is the energy cost only. Shelves, posts, elements, kiln wash and the eventual relining are real and belong in a separate per-firing overhead line before you set a member fee.
Try it: interactive demo
Enter your kiln rating, firing length, electricity rate and the pieces in the load.
Variations
Cost with a duty cycle
A kiln does not draw full power the whole cycle — elements switch off as it holds temperature. Multiply by a measured duty cycle of 0.6–0.8 for a more honest figure.
Break-even firing fee
Add per-firing overhead before dividing, so the fee covers elements and shelves rather than just electricity.
Pitfalls & errors
Nameplate kilowatts is the maximum draw, not the average. Without a duty-cycle factor this calculation overstates cost, often by 25–40% on a long glaze firing with a hold.
Put a cheap energy monitor on the kiln circuit for one firing. One real kWh reading replaces every assumption in this sheet and takes an afternoon.
Do not price a half-empty kiln at the full-load per-piece rate. The firing cost barely moves with load size, so a 20-piece glaze load costs nearly double per piece — that is the argument for waiting a day to fill it.
Practice workbook
Frequently asked questions
Why does a glaze firing cost more than a bisque?
Should I charge members per piece or per firing?
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