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Sauna Heater Sizing - How to Size the Heater to the Room Size

The sauna heater must be sized to the sauna room properly. With the correct sauna heater, the warm-up time should be 20 to 30 minutes. The correct sauna heater warms the wood in the sauna room and also heats the rocks in the sauna heater.
Do not oversize the sauna heater - as the aggressive heat from the heater in operation may feel harsh and unpleasant.

We apply 45 to 47 cubic feet per 1 kilowatt of sauna heater. 50 cubic feet per 1 kilowatt is a conservative conversion advocated by many heater manufacturers.

We use the industry standard height of 7' for the sauna interior. For sauna rooms higher than 7', the additional cubic area requires additional heater output - more than just for the cubic feet - as the heat rises to the top.

Tip - Avoid this Common Mistake:
Never use a GFI or GFCI in the sauna circuit. There is no need for a Ground Fault Circuit Interrupter - it is not required according to the NEC National Electrical Code. It will be troublesome when it keeps shutting off the sauna power whenever water is thrown on to the hot rocks.

Sizing the Most Common Sauna Heaters - to Size the Sauna Room:

A 6 kw heater heats a 7' high room - 5'x7', 6'x7', 5'x6' room sizes - minimum 240 cu ft - maximum 300 cubic feet
A 7.5 kw heater heats a 7' high room - 6'x8', 7'x7', 7'x8' room sizes
- minimum 280 cu ft - maximum 375 cubic feet

Sizing Small Sauna Heaters - for Small Sauna Rooms:

A 3 kw heater heats a 7' high room - minimum 120 cu ft - maximum 150 cubic feet
A 4 kw heater heats a 7' high room - minimum 160 cu ft - maximum 200 cubic feet
A 5 kw heater heats a 7' high room - minimum 200 cu ft - maximum 250 cubic feet


Sizing Large Sauna Heaters - for Large Sauna Rooms:

A 9 kw heater heats a 7' high room - minimum 280 cu ft - maximum 450 cubic feet
A 12 kw heater heats a 7' high room - minimum 480 cu ft - maximum 600 cubic feet


** Sauna Heaters with DEEP ROCK chambers - with extra rocks needs additional time to heat up the rocks - add 1 Kw to the heater size.


Sizing Your Sauna Heater is important - the Sauna Heater must Match the Your Room Size!

How to Calculate Size of a Sauna Heater:
Normal sauna room height should be 7' maximum.

Interior sauna height 78" to 84" - use 1 Kw per 45-47 cu ft.
Interior sauna height 84" to 96" - use 1 Kw per 40 cu ft - heat rises - it takes more Kw to heat up a sauna with interior height of more than 7'.


** A sauna warm-up time of 20-25 minutes is based on a maximum height of 7', the heater correctly sized to the room and the temperature set correctly on the thermostat. A sauna should warm-up in 20 to 25 minutes.

** Sauna Heaters with DEEP ROCK chambers - with extra rocks needs additional time to heat up the rocks - add 1 Kw to the heater size.

Cost of operating a sauna heater is roughly constant - a small heater just takes longer to reach final temperature - it still uses the same electric power over a longer amount of time as compared to a larger heater.




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