What Size Sauna Heater Do I Need?
Heater sizing is primarily a room-volume problem, but raw cubic feet are not the whole story. Glass, tile, brick and other uninsulated surfaces can increase the effective heating load.
Calculate raw room volume first
Multiply interior length × width × height. A 6 × 7 × 7 ft room is 294 ft³ before adjustments.
Match the manufacturer range
Harvia currently rates the 6.0 kW KIP60W for 170–300 ft³. HUUM lists DROP 6 at 177–318 ft³ on 240V. Similar kW labels do not guarantee identical manufacturer sizing ranges.
Adjust for glass and masonry
HUUM’s current US DROP manual says to add 3.3 ft³ of effective room volume for each 1 ft² of uninsulated brick, tile or glass. Use the exact manufacturer method for the heater you are considering rather than one universal rule.
Do not oversize blindly
A bigger heater can change electrical requirements, clearances and control hardware. The goal is not maximum kW; it is the correct listed heater for the room and installation.
Primary sources
Specifications and installation requirements can change. Confirm the current manual for the exact model before purchase or installation.