An indoor traditional sauna is a wooden room with a high-power heater inside it, which makes the electrical work the most important job in the whole install. It’s also the job most buyers know least about.
This article covers what that work involves, so you can brief an electrician well. For what it costs, see the installation cost guide in the home sauna section; for the wider traditional sauna decisions, start with the traditional sauna buying guide.
Short answer: a traditional sauna heater needs a dedicated, hardwired 240V circuit sized to the heater, copper wire rated for 90°C inside the walls, and no GFI on the heater. A licensed electrician does it to the heater manual and local code.
Amps and wire by heater size
| Harvia KIP heater | Amps at 240V | Wire (per manual) |
|---|---|---|
| 4.5kW | 18.8 | #10 |
| 6.0kW | 25.0 | #10 |
| 8.0kW | 33.3 | #8 |
From Harvia’s KIP installation manual (North America). Your electrician sizes the breaker to the heater and local code; cabin makers list theirs too. Almost Heaven lists a 240V/30A circuit for the Sutton and Madison and 240V/40A for the 8kW Bridgeport.
Three details that trip people up
No GFI on the heater. Harvia’s manual states that a ground fault interrupter should not be installed on a sauna heater: it will trip and can cause damage.
Heat-rated wire. The manual calls for copper wire suitable for 90°C inside the sauna walls.
A separate lighting circuit. Many cabins run their lights on 120V. The Almost Heaven Sutton lists a 110V/15A lighting circuit alongside the heater’s 240V/30A.
Questions to ask your electrician
- Does my panel have room and capacity for a new 240V circuit?
- What breaker and wire size will you use for this heater?
- Will you pull the permit and arrange the inspection?
- Where will the disconnect go, if one is required?
- Can you run the lighting circuit at the same time?
Run the numbers yourself
Amps are watts divided by volts. For any heater on 240V, divide the kW by 0.24.
| Heater | Amps at 240V | Example in our catalog |
|---|---|---|
| 4.5kW | about 18.8 | SaunaLife Model X2 (4.5 or 6kW recommended), Finnmark FD-5 Trinity XL |
| 6kW | 25 | Almost Heaven Madison, Sutton, and Salem |
| 8kW | about 33.3 | Almost Heaven Bridgeport, Golden Designs Forssa |
| 9kW | about 37.5 | An option on the Almost Heaven Grandview |
| 10.5kW | about 43.8 | An option on the Almost Heaven Grandview |
Amps are our arithmetic. Heater sizes are from manufacturer and dealer listings, checked September–October 2026.
The breaker is always larger than the running amps, and the manual says how much. That is why a 25A heater goes on a 30A circuit and a 33.3A heater on a 40A circuit.
208V is not 240V
The SaunaLife X2 listing gives its heater requirement as 240V or 208V. Some apartment and commercial buildings supply 208V. A heater built for 240V puts out less heat on 208V, and Harvia’s manual lists separate models for each voltage. If you live in a condo or a converted commercial building, have the electrician measure the supply before you order the heater.
The second circuit, by model
Several cabins need 120V as well as 240V:
- Almost Heaven Sutton and Salem: 110V/15A for lighting.
- Golden Designs Forssa: 120V/15A for lighting and audio controls.
- SaunaLife Model X2: a separate 120V line for lighting.
That is two cables to the sauna, not one. Tell the electrician at the quote stage.
What it costs to run
At full power, a 6kW heater uses 6 kWh an hour, about $1.10 at the 2026 US average of 18.34 cents per kWh. An 8kW heater uses about $1.47. The heater cycles once the room is hot, so a session costs less than the hourly rate suggests.
Where the controls go
For heaters with a separate control, Harvia’s manual says the control panel and power unit must be installed in a dry place, which means outside the hot room. Decide where before the walls are closed.
Before you book the electrician
Here’s what the spec sheet won’t tell you: you should choose the heater first. Moving from a 6kW to an 8kW heater changes the amps, the wire, and possibly the breaker, so quotes made for one won’t fit the other.
Send the electrician the heater’s model number and installation manual. For the cabins in our traditional sauna comparison, each product page lists the circuit the maker specifies.
Bottom line: the heater manual is the electrician’s real instruction sheet. Pick the heater, then hand them the manual.
Sources
- Harvia, KIP electric sauna heater instructions for installation and use (North America), September 17, 2015: almostheaven.net
- Circuit requirements for the Almost Heaven Sutton, Madison, and Bridgeport: manufacturer and Select Saunas listings, checked October 1, 2026
- U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A (residential average 18.34¢/kWh, June 2026 data), accessed October 1, 2026
- Heater sizes and circuits: SaunaLife, Finnmark, Golden Designs, and Almost Heaven listings, checked September–October 2026