How to calculate

A sauna of 200 × 200 × 210 cm has 2.0 × 2.0 × 2.1 = 8.4 m³. By the rule it needs about 8 kW. If it had a 4 m² all-glass front, you add 4 × 1.2 = 4.8 m³, so you size the heater for 13.2 m³.

Table for common sizes

These figures assume wooden cladding and insulated walls. With large glass areas or tiling, increase the output using the rule above.

Three cases that need more output

• Glass, stone, tiling. They do not insulate and lose heat, so they count as extra volume.
• Outdoor sauna without insulation. A barrel has a solid wall but no insulation. In frost it needs more time and energy.
• High ceiling. Every extra 10 cm adds 0.4 m³ in a 2 × 2 m sauna. The optimum is 190–210 cm.

Why not go bigger “just in case”

An oversized heater brings the sauna up fast, switches off, then on again. The temperature swings, the stones never heat evenly and löyly is less pleasant. An undersized heater runs flat out, never really gets there and wears out sooner. What you want is a heater that holds the temperature at about half its output after heat-up.

Electric or wood-burning

An electric heater is convenient: a switch or Wi-Fi, 6 to 9 kW on a 400 V supply with its own breaker. A wood-burning heater needs no electricity and gives softer heat and the atmosphere of a fire, but requires a chimney and tending. It is popular in outdoor saunas and essentially impossible in a flat.

Infrared: emitters, not kilowatts

In an infrared cabin the output is not set by volume but by how many emitters cover the back and legs of a seated person. Four emitters suit a single-person cabin, six a two-person one and eight a three-person one. Rated power is 1.4 to 2.8 kW from a standard 230 V socket.

Supply and safety

• Heaters of 6 to 9 kW: 400 V supply, typically a 3 × 16 A breaker, connected and certified by a qualified electrician.
• A wooden guard rail belongs around the heater, with the manufacturer’s clearances respected.
• Stack the stones loosely so air can flow between them, and re-stack them occasionally.

Frequently asked questions

How long does heat-up take?

With the right heater and an insulated sauna, usually 30 to 60 minutes. Uninsulated outdoor saunas and frosty weather take longer.

How much does the heater consume?

An 8 kW heater about 9 kWh per session – 45 minutes at full power, then roughly half. At €0.25/kWh that is about €2.25.

Can the heater be controlled remotely?

Yes, Wi-Fi control is an option in the configurator. Remote starting has safety rules – nothing flammable may be left inside the sauna.

What about saunas larger than 14 m³?

A 9 kW heater covers roughly 14 m³ including the glass allowance. Heaters above 9 kW are specified individually according to volume, shape and glazed area. Send us the dimensions and we will propose a solution.