ICE & CEDAR

What a sauna actually costs to run

A 6kW sauna, three one-hour sessions a week, at the US average rate: about $8.84 a month. Here's the arithmetic, and here's every assumption inside it.

Last verified · Ice & Cedar editorial

A 6kW sauna used three times a week for an hour costs roughly $8.84 per month at the US average rate of 18.83 cents per kWh — about $0.68per session. The heater’s big kW number frightens people; the hours are what actually bill you.

Monthly cost by heater size

One-hour sessions, heater energised 60% of the time, at 18.83cents per kWh. The kWh column is there so you can substitute your own rate — multiply it by your cents-per-kWh and divide by 100.

HeaterPer sessionkWh / session3×/week5×/week
3 kW$0.341.80$4.42$7.36
4.5 kW$0.512.70$6.63$11.05
6 kW$0.683.60$8.84$14.73
8 kW$0.904.80$11.78$19.64
9 kW$1.025.40$13.25$22.09
10.5 kW$1.196.30$15.46$25.77

Every assumption in that table, stated

This is the part competitors skip, which is precisely why their numbers are not checkable.

  • Duty cycle: 60%. A heater pulls rated power while bringing the room and stones up, then cycles to hold temperature. We assume it is energised about 60% of an hour. We have not metered a sauna— this is a reasoned assumption, not a measurement, and it is the single biggest source of error on this page. A well-insulated room runs lower; an uninsulated one runs higher.
  • Session length: 60 minutes, covering heat-up plus sitting. Shorter sessions do not scale down linearly, because heat-up is the expensive part and it is fixed.
  • Rate: 18.83 cents per kWh— the EIA US residential average for April 2026. Almost certainly not your rate.
  • 4.345 weeks per month. The actual average, rather than a tidy 4.

The arithmetic, for the 6kW row

6,000W ÷ 1,000 = 6 kW. Times 1 hour = 6 kWh at full draw. Times a 0.6 duty cycle = 3.60 kWh per session. At 18.83 cents that is $0.68 per session. Three sessions a week × 4.345 weeks = 46.9 kWh per month = $8.84.

Check it with your phone. That is the point of printing it.

What this means for the purchase

Running cost is not the constraint on a home sauna — the circuit is. Twenty dollars a month does not change anyone’s decision; a $1,200 panel upgrade does.

Which reframes the heater-size question usefully. The gap between a 6kW and a 9kW heater is roughly $4.42 a month in electricity and a materially bigger circuit up front. Size the heater to the room, not to the running cost.

Frequently asked questions

How much does it cost to run a sauna per month?

A 6kW sauna used three times a week for an hour costs about $8.84 a month at the US average electricity rate of 18.83 cents per kWh, assuming the heater is energised about 60% of the session. Your rate is the variable that matters most: the same sauna in North Dakota (12.35 cents) costs roughly a third less than in Hawaii (46.62 cents).

What's the duty cycle assumption and why does it matter?

A sauna heater does not draw rated power for the whole session. It pulls hard while heating the room and stones, then cycles on and off to hold temperature. We assume it is energised about 60% of an hour-long session. That is an assumption, not a measurement — we have not metered a sauna. If your room is well insulated the real figure is lower; if it is uninsulated or you throw a lot of water, it is higher. We state it so you can adjust it rather than hiding it inside a number.

Does a bigger heater cost more to run?

Per hour of energised time, yes — proportionally to kW. But it is not a clean multiplier in practice, because a correctly-sized bigger heater reaches temperature faster and then spends more of the session cycling rather than pulling. An undersized heater in a large room can cost more than an oversized one because it never stops trying. This is one reason we always round heater sizing up.

Is a sauna expensive to run compared to other appliances?

Less than most people expect. A 6kW sauna three times a week lands in the same monthly range as a modest appliance habit — noticeably less than an electric vehicle and far less than the purchase price would suggest. The heater's high kW is alarming on paper because it is a large number; what matters is that you run it for a few hours a week, not continuously.

Should I use the national average rate?

No, and we would rather you didn't. We use it as a default because we have to use something, but 18.83 cents is the US average, and the same EIA table has North Dakota at 12.35 and Hawaii at 46.62. Your bill has your actual rate on it. Multiply the kWh column by your own number — that is why the kWh column is there.

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