What a session uses
For a typical indoor home sauna (6–8 m³, 6–8 kW heater) the model gives about 4–5 kWh to heat up and 2–3 kWh per hour of bathing, so roughly 6–8 kWh for heat-up plus an hour. At the average household price that is:
| Country | Price per kWh (default) | ≈ 7 kWh session |
|---|---|---|
| United States | $0.18 (EIA, July 2026) | ≈ $1.30 |
| United Kingdom | £0.26 (Ofgem cap, Oct–Dec 2026) | ≈ £1.85 |
| Germany | €0.36 (Eurostat, 2026-S1) | ≈ €2.55 |
| Netherlands | €0.24 (Eurostat, 2026-S1) | ≈ €1.70 |
| Sweden | SEK 3.30 (Eurostat, 2026-S1) | ≈ SEK 23 |
| Poland | PLN 1.27 (Eurostat, 2026-S1) | ≈ PLN 8.90 |
Outdoor saunas use more in winter: a 6 ft barrel at −10 °C (14 °F) needs about a third more energy to heat up than at +5 °C (41 °F).
How the model works
The sauna is simulated every few seconds as connected heat stores: the air, the heater with its stones, and each wall layer (wood panel, insulation, outer board or the solid wood of a log or barrel wall), plus glass, the door and the floor. Heat leaves through the walls and with the ventilation air (about 6 air changes per hour, as makers recommend, more while people go in and out). The thermostat sits at ceiling height and switches the heater on and off around your target.
Results are estimates: real use depends on the stones, the airflow and how often the door opens. We show them as ranges and list the assumptions.
How to spend less
- Keep the door shut and don't over-ventilate (but never block the vents).
- A wooden door instead of glass, and insulation in walls and ceiling.
- Don't heat higher than you use: 70 °C instead of 90 °C saves a noticeable share of the heat-up energy.
- Bathe right after heat-up instead of leaving the heater on for hours.