Sauna heaters are matched to room volume. As a rule of thumb you need about 1 kW of heater power for every 45–50 cubic feet of sauna interior. Measure your room's length × width × height, then round up to the nearest available heater size. A glass door, glass wall or uninsulated (outdoor / solid-log) walls all lose heat and require more power — the calculator above adds that load automatically.

Yes. Glass radiates far more heat than an insulated wall. Following Harvia and HUUM's published charts, roughly 1.2 m³ (about 42 cu ft) of extra heating load is added per square meter of glass or uninsulated surface. A standard glass door adds a modest amount; a full glass front or large window adds significantly more. Check the boxes in the calculator to include this.

An oversized heater heats faster but can cycle harder and use more energy than needed; an undersized one struggles to reach and hold 175–195°F. The goal is a heater whose rated volume range comfortably covers your room. The calculator recommends the best-fit size and shows a step up for extra headroom (useful for cold climates or frequent quick heat-ups).

Every electric heater needs a control unit and sauna stones, and must be wired by a licensed electrician to the correct voltage (most 6 kW+ heaters need 240V, single or three-phase). Our heater packages bundle the heater, control and stones together. Talk to a specialist to confirm the electrical requirements for your model.

It uses the same volume-based method Harvia and HUUM publish and is an accurate starting point for the vast majority of home saunas. For unusual ceilings, commercial rooms, or borderline sizes, have our team confirm the final selection against the manufacturer's chart for your exact model — it's free.