The calculations
- Heater size uses each maker's own room range and the effective-volume rule from heater manuals (+1.2 m³ per m² of glass, tile, stone or concrete; × 1.5 for solid log walls, which we also apply to barrel staves).
- Heat-up time and running cost come from a heat model of the room: air, heater and stones, and every wall layer are simulated every few seconds, with ventilation and a thermostat at the ceiling. It is calibrated so a heater sized by its maker reaches 80 °C in roughly 30–60 minutes, as manuals describe. Results are estimates and shown with their assumptions.
- Cold plunges and hot tubs use the heat balance of the water: heat through the shell and lid, body heat, pumps, and the chiller's or heater's output.
- Electricity prices are official averages per country (Eurostat, U.S. EIA, Ofgem, ElCom, MBIE) with their date; you can always enter your own.
- Climate defaults are monthly mean temperatures from national met services.
The product facts
Every spec on a product page comes from the maker's product page, its manual or a retailer listing, and the source is linked with the date it was read. If a value is not published, we say so instead of guessing. We do not use sites whose robots.txt asks AI agents not to read them.
How Saunoka earns money
Saunoka is free. When you buy through a shop link we may earn a commission from the shop, at no extra cost to you. We may also sell a detailed DIY build pack, and offer manufacturers a planner for their own websites. Commission never changes a ranking: lists are ordered by fit and value for your room.
What we never do
No invented products, prices, reviews or "people bought" counters. No medical claims. No DIY wiring instructions: electric heaters are installed by licensed electricians.