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10.5 kW Sauna Heater: Breaker, Wire & Cost
The direct answer first, then the full NEC math and how run length changes the wire.
| Continuous load (×1.25, NEC 210.20(A)) | 54.7 A |
|---|---|
| Breaker (NEC 240.6) | 60 A |
| Copper wire, 75°C (NEC 310.16) | 6 AWG |
| Cost to run | ~$28.98/mo |
Wire size by run length (voltage drop ≤ 3%)
| One-way run | Copper wire | Voltage drop |
|---|---|---|
| 25 ft | 6 AWG | 0.45% |
| 50 ft | 6 AWG | 0.9% |
| 75 ft | 6 AWG | 1.34% |
Longer runs need thicker copper so the heater still sees full voltage. Aluminium and 60°C terminations change these numbers, confirm with your electrician.
Try your own numbers
Heaters at 10.5 kW (240V)
Three heaters that fit at 10.5 kW, each flagged with its standout spec so you can choose on more than price. From our cross-brand database, not by what pays most. See all heaters › or compare models ›
FAQ
What size breaker for a 10.5 kW sauna heater?
A 10.5 kW heater on a 240V circuit draws 43.8 A. Because a sauna runs for hours at a time, the NEC counts it as a continuous load (NEC 210.20(A)) and requires the breaker sized at 125% of the current, or 54.7 A, which rounds up to the next standard size (NEC 240.6): a 60 A breaker. Do not down-size to the running amps to save on wire; the 125% rule is what stops the breaker nuisance-tripping and the terminations overheating. On a 208V supply (common in apartments and commercial buildings) the same heater draws 50.5 A and wants a 70 A breaker instead.
What gauge wire for a 10.5 kW sauna heater?
6 AWG copper rated for 75°C carries the 60 A circuit on a short run. Two things force a heavier gauge: distance and metal. Past roughly 50–100 ft the voltage drop climbs above 3% and the heater quietly underperforms, so you step up a size (the table above shows the exact crossover for this heater). Aluminium conductors and 60°C-rated terminations also carry less, so they need upsizing too. Match the ground/EGC to the breaker per NEC 250.122.
How much does a 10.5 kW sauna heater cost to run?
Roughly $28.98 a month if you run it three times a week for a ~45-minute session plus heat-up, at $0.17/kWh. It is cheaper than most people expect because the elements only pull the full 10.5 kW while heating up; once the room hits temperature the thermostat cycles them on and off, so the back half of every session sips power. A well-insulated room with a closed door during pre-heat is the biggest saving. The running-cost calculator lets you put in your own rate and session habits and compare heater sizes side by side.