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Size the heater, not the guess.
An undersized heater never reaches löyly; an oversized one scorches the air before the walls warm. Give us the room — we’ll give you the kilowatts and the kit.
01 — The room
02 — Glass
03 — Walls
04 — Placement
Your room asks for
9.5 kW
8.3 m³ room · effective load 9.1 m³ after glass, walls and climate.
Recommended kit
10.5 kW Wi-Fi Heater Kit
Large rooms and panoramic glass without breaking a sweat — well, yours excepted.
Estimate only — your quote confirms it against wiring and climate.
The arithmetic of löyly.
01
One kilowatt per cubic metre
The Nordic rule of thumb: a well-built room wants ~1 kW per m³ to hold 85–95°C with steam headroom.
02
Glass and cold walls tax it
Every square metre of glass behaves like an extra 1.2 m³ of room; uninsulated timber and outdoor placement add their own surcharge.
03
Then we round up, once
Heaters live longest one size above the minimum — lower element stress, faster recovery after the door opens.
Let a human check the math.
Send the numbers with your quote — a consultant confirms the kit against your wiring, climate and stove taste. Wondering about the bill? Run the running-cost calculator →
Request a quote