Sauna power consumption: what a sauna session really costs

The simple formula: kilowatts times hours times electricity price

Hardly any question preoccupies sauna prospects as much as the electricity bill, and hardly any can be answered so cleanly. Sauna power consumption follows a simple formula: the device's power in kilowatts times the running time in hours gives the consumption in kilowatt hours. Multiplied by your electricity price per kilowatt hour, the amount in euros is the result. No more maths is needed; a glance at the rating plate and at your last electricity bill is enough.

For all worked examples in this article we assume an electricity price of 35 cents per kilowatt hour. This is a deliberately chosen assumption in the range of typical household tariffs, not a measured value and not a guarantee: your actual unit price is on your electricity bill and may be lower or higher. If you pay around 30 cents, for instance, you subtract about one seventh from our results; at 40 cents you add correspondingly.

One important subtlety right away: the power on the rating plate is the maximum power. A sauna heater or an infrared emitter does not run at full power for the whole session but is cycled by the controller once the target temperature is reached. Anyone who simply multiplies the rating plate by hours therefore almost always overestimates consumption. This is exactly where many estimates online fail, making a sauna evening look artificially expensive.

Worked example, infrared cabin: well under 1 euro per session

A typical infrared cabin for two people draws around 2 kilowatts, while compact single cabins are more in the range of 1.3 to 1.7 kilowatts. Let us deliberately calculate generously with a 45-minute session including preheating and full power throughout: 2 kilowatts times 0.75 hours gives 1.5 kilowatt hours. At our assumed electricity price of 35 cents per kilowatt hour, that is just over 52 cents per session, so less than an espresso in a café.

In practice the figure is often even lower, because many cabins throttle down after the preheating phase. Even if you sweat every second day, you stay at a manageable 8 to 10 euros a month. The infrared cabin is by far the cheapest way to sweat regularly at home; our infrared cabin buying guide shows which designs and heater types exist. Whether the mild radiant heat is enough for you, or you want the classic sauna climate with infusions, is answered by our fundamental comparison Infrared cabin or sauna.

Worked example, home sauna: the 9 kW heater calculated honestly

The wildest figures circulate for the classic 9 kW heater, so we calculate honestly. The heater draws close to full power continuously only while heating up; depending on cabin size, insulation and starting temperature, this phase takes about 30 to 45 minutes. After that the controller takes over: it switches the heating elements on only in phases to hold the target temperature. In these holding phases the power actually drawn drops significantly, because a well-insulated room does not lose heat as fast as a 9 kW heater could replace it.

For a complete sauna evening with heating up and two to three rounds, roughly 5 to 8 kilowatt hours are therefore realistic. This is explicitly a rough estimate: a compact, well-insulated cabin in a heated basement sits at the lower end, a large cabin with thin walls, a long evening and a frequently opened door sits above it. At 35 cents per kilowatt hour that comes to €1.75 to €2.80 per sauna evening. If two or three people share the heat, the amount per head drops significantly again.

Important for planning: a 9 kW heater needs a 400 volt three-phase connection, which an electrical contractor installs. For small cabins there are alternatively compact 3.6 kilowatt heaters for the standard socket; they heat more slowly but manage without three-phase power. Our overview of 230 volt sauna heaters shows the differences, the large sauna heater guide explains which heater class suits which cabin size, and our home sauna overview gathers suitable cabins for indoors.

Worked example, garden sauna: winter makes it more expensive

The garden sauna follows the same rules, only under harsher conditions. In winter the heater starts at outside temperatures around or below zero, the walls constantly give off heat to the cold surroundings, and every opening of the door costs noticeably more than in a heated basement. The result: heating up takes longer, the holding phases get shorter, and the heater cycles back to full power more often.

As a rough estimate we calculate 8 to 12 kilowatt hours for a winter sauna evening in a garden house, which is €2.80 to €4.20 at our example price of 35 cents per kilowatt hour. In summer, by contrast, the garden sauna moves closer to the values of the indoor cabin again. How widely your setup varies depends mainly on wall thickness, seals and location; what to look for when buying is covered in our garden sauna guide.

Six savings levers that really make a difference

You can do little about the electricity price itself, but all the more about consumption. These six levers have the biggest effect in practice:

• Take insulation and wall thickness seriously: A thick-walled, tightly closing cabin keeps the heat where it belongs. For garden saunas, wall thickness is the most important saving criterion of all, because every kilowatt hour saved here counts evening after evening.
• Keep the ritual tight: Shower first, then go in, and plan the rounds back to back. A heater that keeps heating for an hour between rounds because someone is still on the phone burns money for nothing. Closing the door promptly is part of it too.
• Several people per heater: Whether one or three people sweat makes almost no difference to consumption. Shared sauna evenings halve or third the cost per head.
• Do not overdo the target temperature: Between 75 and 85 degrees most people find sauna bathing more pleasant than at 100 anyway. Every degree less shortens heating up and lengthens the heater's breaks.
• Time the heating-up wisely: Start the heater only when your evening really begins, instead of letting it run on speculation. A timer or app control helps to set the start precisely.
• Check your tariff: Anyone who uses a sauna regularly should know their own unit price and compare tariffs. A green electricity tariff also makes the sauna evening more climate-friendly, often at no extra cost.

Comparison table: rough costs per session

All values are worked examples with an assumed electricity price of 35 cents per kilowatt hour, rounded and intended as a guide:

The ranges arise from cabin size, insulation, outside temperature and your personal ritual. If in doubt, measure it yourself: a sub-meter for the supply line costs little and ends every discussion with real figures.

Conclusion: electricity is not the cost driver

When it comes to saunas, the fear of the electricity bill is usually bigger than the bill itself. An infrared session costs around 50 cents in our worked example, a complete sauna evening with a 9 kW heater rarely more than 3 euros, and even winter operation in the garden stays below the entry price of any public thermal spa. The real cost driver is the purchase, not the running. Anyone who plans insulation and heater choice carefully and bundles their ritual saunas at home surprisingly cheaply. You will find more background knowledge on planning, technology and sauna practice in our guide section.