How much does a sauna cost to run in the UK?

A 6kW traditional sauna costs about £1.57 per session to run, and a 1600W infrared cabin about 42p. Those are the two numbers most people are looking for, and almost nobody publishes them. Sellers quote the purchase price and go quiet on the standing cost, which is the one that decides whether a sauna gets used three times a week or three times a year.

Both figures use the Ofgem price cap for 1 July to 30 September 2026, which sets electricity at 26.11p per kWh for a standard variable tariff paid by direct debit. Swap in your own unit rate and the arithmetic below still works.

The short answer, by sauna type

A session here means one heat-up plus about an hour of use. That is not the same as running the heater flat out for an hour, and the difference matters, which is the next section.

Why the heater's rating is not what you pay for

A 6kW heater does not draw 6kW for as long as it is switched on. It draws full power while bringing the cabin up to temperature, then the thermostat starts cutting it in and out to hold the setpoint. Duty cycle after that point is typically 30% to 50%, depending on insulation and outside temperature.

For a 6kW outdoor cabin that works out at roughly 4 kWh for a 40 minute heat-up, then about 2 kWh across an hour of cycling. Six units, £1.57. A poorly insulated cabin in January pushes the second number up, not the first, because the heat-up is fixed work and the holding is where the losses show. Getting the output right in the first place matters here too, since an undersized heater never stops running at full power.

This is the reason wall construction earns its place in how we rank outdoor cabins. A 45mm thermowood wall holds temperature with the heater off for longer than a thin panel, and that gap is paid for every session for the life of the cabin.

Infrared is cheaper because it heats you, not the room

An infrared cabin runs at 30°C to 65°C rather than 80°C to 100°C, and it gets there with panels rated in hundreds of watts rather than kilowatts. A 1600W two-person cabin drawing full power for a full hour costs 42p, and in practice it draws less than that once it settles.

Over a year the gap is the entire argument for the category. Three sessions a week in a 6kW cabin is about £245. The same routine in an infrared cabin is about £66. That is a £179 a year difference, which pays back a chunk of the purchase price on its own.

What actually moves the number

Cabin volume, not floor area

Heaters are sized on cubic metres, so a cabin with a high ceiling costs more to run than its floor plan suggests. Manufacturers publish a volume range per heater output for exactly this reason, and Harvia, which makes more sauna heaters than anyone else, lists one for every model. Buying a heater at the bottom of its range means it runs at full power for longer.

Where the cabin sits

An outdoor cabin in a British February loses heat to the air, the wind and the ground. An identical cabin in a spare bedroom loses very little, which is why the same heater output goes further indoors. If running cost is the deciding factor rather than capacity, that argues for an indoor cabin over a garden build, which also avoids the height limits the Planning Portal sets for garden outbuildings.

How you heat up

Two shorter sessions in one evening cost far less than two sessions on separate days, because the second one skips the heat-up entirely. Households sharing a sauna back to back get the cheapest sessions available.

Wood instead of electricity

A wood-fired stove takes the running cost off the electricity bill and puts it in logs. A session burns roughly 10kg to 15kg of dry hardwood, which at typical UK kiln-dried prices is £4 to £7. That is more than the electric equivalent, and people who choose it are buying the fire, not the economics. Whether you can burn wood at all depends on your address, which is the first thing the wood against electric comparison establishes.

The costs that are not the heater

Running cost is not the whole standing cost, and the rest is easy to leave out of a budget. The electrical line is the one that is fixed rather than optional, because a new circuit is notifiable work under Approved Document P of the Building Regulations and has to be certified:

• Electrical installation for a traditional heater: a dedicated certified circuit is £300 to £800 depending on the run from the consumer unit
• Wood treatment on an outdoor cabin: a breathable treatment every year or two, and on many cabins skipping it voids the warranty
• Stones: replaced every few years as they crumble, £40 to £80 a set
• Heater lifespan: an element is a consumable, and a domestic heater lasts roughly 10 to 15 years of regular use

Working out your own number

The calculation is short enough to do on a phone. Take the heater rating in kilowatts, multiply by the hours it runs at full power during heat-up, then add the session length multiplied by the rating multiplied by 0.4 for the cycling. Multiply the total by your unit rate.

1. Heat-up: 6kW × 0.67 hours = 4 kWh
2. Session: 6kW × 1 hour × 0.4 duty cycle = 2.4 kWh
3. Total: 6.4 kWh × 26.11p = £1.67

That is the pessimistic version of the same session we costed at £1.57 above, and the gap between the two is the honest margin of error on any figure like this. Anyone quoting sauna running costs to the penny is guessing at your insulation.