SaunaCosts

Sauna electrical requirements calculator

A sauna heater runs for hours at a time, which makes it a continuous load. The National Electrical Code sizes both the wire and the breaker for a continuous load at 125 percent of its current draw, so a heater pulling 25.0 amps needs a 35 amp circuit rather than the 25 amp one the arithmetic alone suggests. That gap is where most planning goes wrong.

Your circuit

Current draw
25.0 A
Minimum breaker
35 A
Minimum copper wire
8 AWG

Wire sizes are the 60 degree C copper column of NEC 310.16, the column that governs terminations on ordinary residential breakers. This is a planning figure. Circuit length, ambient temperature, conduit fill, aluminum conductors and your local amendments all change the answer, and the install has to be signed off by a licensed electrician who has seen the actual run.

Common 240 V circuits at a glance

HeaterDraw at 240 VBreakerCopper wireBreaker at 208 V
3 kW12.5 A20 A12 AWG20 A
4.5 kW18.8 A25 A10 AWG30 A
6 kW25.0 A35 A8 AWG40 A
8 kW33.3 A45 A6 AWG50 A
9 kW37.5 A50 A6 AWG60 A
10.5 kW43.8 A60 A4 AWG70 A
12 kW50.0 A70 A4 AWG80 A

Common 120 V heaters at a glance

Plug in models run on a standard household supply. Note that even at this size the continuous-load rule pushes most of them onto a dedicated 20 amp circuit rather than sharing a general-purpose 15 amp one.

HeaterDraw at 120 VBreakerCopper wire
1.5 kW12.5 A20 A12 AWG
1.8 kW15.0 A20 A12 AWG
2 kW16.7 A25 A10 AWG

Models that run on 120 volts: 120 volt plug in saunas. Most still want a dedicated circuit rather than a shared one: the continuous-load rule puts a 2.4 kW heater on 25 amps and a 2.8 kW one on 30, neither of which is an ordinary household outlet. To size the heater itself first, use the heater sizing calculator.

Sauna electrical questions

What breaker does a 6 kW sauna need?
A 6 kW heater on 240 volts draws 25.0 amps. A sauna is a continuous load, so NEC 210.20(A) sizes the breaker at 125 percent of that, which is 31.3 amps, and the next standard breaker up is 35 amps. The conductor has to carry that too, which puts it at 8 AWG copper.
How do I convert sauna kW to amps?
Amps equal watts divided by volts, so kW times 1,000 divided by the supply voltage. A 9 kW heater at 240 volts is 9,000 divided by 240, or 37.5 amps. That is the draw, not the circuit size: multiply by 1.25 for the continuous-load rule before choosing a breaker, which puts a 9 kW heater on a 50 amp circuit.
Why is the breaker bigger than the heater's amp draw?
Because a sauna runs for hours rather than minutes. The National Electrical Code treats any load running three hours or more as continuous and requires both the conductor and the overcurrent device to be rated at 125 percent of it, so the circuit is not sitting at its own limit for the whole session.
Can a sauna run on a normal household outlet?
Some can. Heaters around 1.5 to 2 kW run on 120 volts, though the continuous-load rule still puts most of them on a dedicated 20 amp circuit rather than a shared 15 amp one. The 120 volt plug in saunas list shows every model in the catalog whose maker specifies 120 volts and no 240 volt circuit.
What wire size does a sauna heater need?
It follows the breaker, not the heater. The table above uses the 60 degree C copper column of NEC 310.16, which is what 110.14(C)(1)(a) requires on circuits of 100 amps or less unless the terminations are listed for a higher temperature, and on ordinary residential breakers they are not. Longer runs, hot attics, crowded conduit and aluminum conductors all push the size up, so treat these as the floor and have the run assessed before buying wire.

Prices and specifications verified July 25, 2026, and re-checked weekly after that. How these numbers are checked.

Free guide: sizing and budgeting a home sauna

A fill-in worksheet covering room sizing math, the electrical checklist, indoor vs outdoor decisions, a full cost worksheet, and ten questions to ask the dealer.