Sizing an electric sauna heater? Here’s why 9kW is your max

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When building a sauna with an electric sauna heater, it is critical to choose the right sauna heater. Most everybody puts their focus on the hot room, but generally speaking, the main reason why 9kW is your maximum size electric sauna heater has nothing to do with your hot room.

Want to guess why 9kW is your max size for home saunas?

Here’s a clue:

Electric service panel, with room for an electric sauna heater

Yep, you got it. The control panel. Homes in North America are single phase electric. Power comes in from the power company right to the electrical box. We can draw off power for appliances like clothes washers, arc welders, and power amps for heavy metal guitarists in the form of a dual breaker 20 amp circuit. 20 amp +20 amp = 40 amps. That’s good! We start pushing beyond this, and well, appliances can start tripping (without Psilocybin).

a 40 amp double pole breaker – recommended for electric sauna heater applications, wired directly to the control panel

Now, when it comes to firing up our home saunas with electric sauna heaters (an oxymoron, I know) if we start trying to log jam a commercial electric sauna heater into our residential saunas, well, chances are you’ll be seeing colors and trails from your trips to the control panel to reset your circuit breaker.

Good news when it comes to electric sauna heater sizing

9kW is your max. And 9kW is a great size for most all residential applications. And 9kW is the max that sauna heater manufacturers UL certify. You can refer to sizing charts on sauna heater manufacturer websites. What you will find is that a 9kW fits a 6’x8′ or 7’x7′ or even an 8’x8′ hot room like a baseball glove (and not an OJ Simpson glove). To best understand sauna heater sizing, consider that a an electric sauna heated sauna performs best when the stove is “on” no more than 30% of the time. Like Goldilocks and porridge:

A sauna heater undersized for your hot room will:

  • be on too much.
  • suck the oxygen out of the room.
  • overheat the rocks and your ears.
  • give löyly that will make you want to rush out the hot room door.
  • be apt to provoke your guests to say “This sucks. I don’t like sauna.”
  • incur increased energy consumption: the heater runs more frequently.

A sauna heater oversized for your hot room will:

  • be on too little.
  • heat the room too fast.
  • underheat the rocks, and your body, and your soul.
  • give löyly that will make you feel like a wet diaper (wimpy and wet).
  • be apt to provoke your guests to say “This sucks. I don’t like sauna.”

Do you get the idea of how important this is? 9kW is the max for residential purposes. Let’s size our hot rooms and heaters appropriately.

A 6kW electric sauna heater well sized for the hot room (and the home service panel!).

Editor’s note: There’s always the potential for a bigger hammer. You’ll sometimes find commercial sized electric sauna heaters in residential homes, especially newly built mega homes with big ass basements that go on and on. In these instances, the electrician will need to install an 80 amp breaker to carry the load of a 15kW sauna heater, for example.

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