Calculators / Hot tubs, saunas and plunges
What size sauna heater do you need?
Put in the inside of the room. You’ll get the heater size, the circuit it needs and the running cost.
Updated · How we check our numbers
Heater for your sauna
6 kW heater
210 ft³ inside, counted as 265 ft³ for glass. It draws 25 A at 240 V.
- Room
- 265 ft³
- Circuit
- 30 A, 10 AWG
- At most
- $21/mo3×/wk, 1.5 h, full power
Estimate for planning only, not professional advice. Check the manufacturer’s instructions, your local code and a licensed professional before you buy, build or install. Use at your own risk. Terms.
volume = 6 × 5 × 7 = 210 ft³
+ 14 ft² glass × 3.9 (Harvia)
Heaters by size
265 ft³- 4.5 kWAmerec 100–210, HUUM 106–247 ft³; 18.8 A at 240 V, 30 A breaker, 10 AWGToo small
- 6 kWAmerec 175–310, HUUM 177–353 ft³; 25 A at 240 V, 30 A breaker, 10 AWGPick
- 7.5 kWHUUM 247–424 ft³; 31.3 A at 240 V, 40 A breaker, 8 AWGAlso fits
- 8 kWAmerec 250–425 ft³; 33.3 A at 240 V, 8 AWGAlso fits
- 9 kWHUUM 282–530 ft³; 37.5 A at 240 V, 50 A breaker, 8 AWGToo big
Room ranges and wiring from Amerec and HUUM manuals. Running cost assumes full power the whole time; thermostats cut it.
HUUM and Amerec wire 6 kW on 10 AWG with a 30 A breaker. Saunacore sizes wire to 80% of its rating, which puts 6 kW on 8 AWG and 40 A. Your electrician and the heater’s own manual decide.
Measure the inside. Redwood Outdoors lists its 6-person barrel at 140 cu ft with a 6 kW heater; Amerec’s and HUUM’s 6 kW tables start at about 175 ft³.
How we work it out
room = length × width × height, + about 3.9 ft³ per ft² of glass, × 1.5 for log walls
Heater makers size by cubic feet. Harvia adds 1.2 m³ for every square meter of glass or uninsulated wall (about 3.9 ft³ per ft²), and multiplies a log sauna by 1.5; HUUM adds a bit more, 1.5 m³ per m². Then we match the room to Amerec's table (4.5 kW for 100 to 210 ft³, 6 kW for 175 to 310, 8 kW for 250 to 425) and HUUM's (4.5 kW for 106 to 247, 6 kW for 177 to 353, 7.5 kW for 247 to 424, 9 kW for 282 to 530).
Wiring is the maker's: HUUM puts 4.5 and 6 kW on a 30 A breaker with 10 AWG, 7.5 kW on 40 A with 8 AWG and 9 kW on 50 A with 8 AWG. Saunacore's manual sizes wire to 80% of its rating, which would put 6 kW on 8 AWG. Have an electrician follow your heater's manual.
Where the numbers come from
Guides
Sauna
More calculators
- Hot tubCan my deck hold it, and can my panel power it?
- Hot tub running costWhat does a hot tub cost to run?
- Hot tub costWhat does a hot tub cost installed?
- Cold plunge chillerWhat size chiller for my cold plunge?
- Sprinkler zonesHow many zones will my water pressure run?
- Water pressure and flow testWhat gpm and psi does my hose bib give me?
- Sprinkler layout plannerWhere do the heads go, and how many?
- Sprinkler run timeHow many minutes should each zone run?