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Sauna electrical requirements

An electric sauna heater needs its own circuit. In North America that is a 240 V circuit; in most of Europe larger heaters run on 400 V three-phase. Here is the current, the usual breaker or fuse and the cable range for your heater, as a brief for a licensed electrician.

Updated Oct 17, 2026

The numbers for common heaters

Heater240 V single-phase (US/CA)230 V single-phase (EU/UK)400 V three-phase (EU)
4.5 kW18.8 A → 25 A breaker19.6 A → 20–25 A6.5 A per phase → 3 × 10 A
6 kW25 A → 35 A breaker26.1 A → 32 A8.7 A per phase → 3 × 10 A
8 kW33.3 A → 45 A breaker34.8 A → 40 A11.5 A per phase → 3 × 13–16 A
9 kW37.5 A → 50 A breaker39.1 A → 40 A13 A per phase → 3 × 13–16 A

Current = power ÷ voltage (three-phase: power ÷ (√3 × 400 V)). In the US, electricians size a fixed heater's circuit as a continuous load at 125% of its current (NEC 424.4(B)), then round up to a standard breaker. The heater's own manual has the final word on breaker, cable and the controller's wiring.

What to tell your electrician

  1. Heater model, kW, voltage and phase, and the manual's breaker and cable table.
  2. Where the heater and the controller go, and the cable length from the panel.
  3. Whether your panel has room for a 2-pole 240 V breaker (US/CA) or a three-phase supply (EU).
  4. Heat-resistant cable inside the hot room, as the manual requires (often silicone-insulated).

We never give DIY wiring steps: sauna heaters are high-current, hot and in a damp room, and most countries require a licensed electrician and often a permit.

Questions and answers

What breaker does a 6 kW sauna heater need?

At 240 V it draws 25 A; sized as a continuous load at 125% that is 31.25 A, so usually a 35 A or 40 A two-pole breaker with the wire size from the manual (often 8 AWG copper). In Europe a 6 kW heater on 400 V three-phase usually uses 3 × 10 A fuses.

Can a sauna run on a normal 120 V outlet?

Traditional heaters, no: they need 240 V. Some small infrared cabins and blankets plug into 120 V outlets, but they are not traditional saunas.

Do I need three-phase power for a sauna in Europe?

Not always. Many heaters up to about 6–8 kW can be wired single-phase at 230 V (with a 25–40 A circuit), but three-phase spreads the load and is usual for 8 kW and above. Check the heater's connection table.

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