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3 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)) | 15.6 A |
|---|---|
| Breaker (NEC 240.6) | 20 A |
| Copper wire, 75°C (NEC 310.16) | 14 AWG |
| Cost to run | ~$8.28/mo |
Wire size by run length (voltage drop ≤ 3%)
| One-way run | Copper wire | Voltage drop |
|---|---|---|
| 25 ft | 14 AWG | 0.82% |
| 50 ft | 14 AWG | 1.63% |
| 75 ft | 14 AWG | 2.45% |
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 3 kW (240V)
Three heaters that fit at 3 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 3 kW sauna heater?
A 3 kW heater on a 240V circuit draws 12.5 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 15.6 A, which rounds up to the next standard size (NEC 240.6): a 20 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 14.4 A and wants a 20 A breaker instead.
What gauge wire for a 3 kW sauna heater?
14 AWG copper rated for 75°C carries the 20 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 3 kW sauna heater cost to run?
Roughly $8.28 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 3 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.