Here is the number everyone actually wants: at the current energy price cap, running a 6.8 kW electric sauna heater flat out for a full hour costs about £1.79. That figure assumes the heater never pauses, which it does in practice, so treat it as the ceiling rather than the bill. Everything below shows where the number comes from, lets you recalculate it for your own tariff, and explains what we deliberately leave out.
The three numbers that decide your running cost
Sauna running cost has no mystery in it. Multiply three things together:
- heater power in kilowatts. The Harvia PC70 fitted in The Cabin Three electric is rated at 6.8 kW
- time the heater draws power, in hours, including warm-up
- your electricity unit rate in pence per kWh. Under the Ofgem price cap the average Direct Debit rate for 1 October to 31 December 2026 is 26.32p per kWh
So the ceiling for one hour: 6.8 kWh × 26.32p = £1.79. A generous 90-minute session, warm-up included, tops out at 10.2 kWh, or £2.68.
Why the real bill comes in under the ceiling
An electric sauna heater does not draw full power for the whole session. Once the hot room reaches the set temperature, the thermostat starts cycling the elements off and on to hold it, and during those off periods the meter rests. How much it rests depends on the outdoor temperature, how often the door opens and how the room breathes, so we publish the flat-out ceiling instead of promising a duty cycle we have not measured for this exact cabin. Budget on the ceiling and let reality undercut it.
What a month looks like
Worst-case figures at the capped 26.32p rate, 90 minutes per session:
| Habit | Sessions per month | Energy ceiling | Cost ceiling |
|---|---|---|---|
| Weekly ritual | 4 | 40.8 kWh | £10.74 |
| Twice a week | 9 | 91.8 kWh | £24.16 |
| Almost daily | 26 | 265.2 kWh | £69.80 |
For scale: even the almost-daily habit lands near the price of a single mid-range gym membership, and the weekly ritual costs less than two coffees.
Work it out for your tariff
Edit any field. The calculator runs in your browser and sends nothing anywhere.
Per session: £2.68 · per week: £5.37 · per month: £23.26
The calculation multiplies power by hours by your rate, nothing cleverer. Standing charges are excluded on purpose: you pay them whether or not the sauna exists, so they belong to your house, not to the heater.
What we deliberately do not claim
You will find sauna sellers quoting exact warm-up times and promising session temperatures. We publish neither for The Cabin Three, because the supplier has not run a verified test for this exact cabin, and warm-up varies with the weather, the starting temperature and how the room is vented. The honest version: the ceiling maths above already includes the warm-up period inside the session time, so the number cannot surprise you in the wrong direction.
Trimming the bill
- Share sessions back to back. The second person's session inherits a hot room, and the thermostat does far less work.
- Check your tariff for cheaper off-peak windows. An evening sauna on a time-of-use tariff can cost noticeably less than the capped daytime rate.
- Keep the door shut between turns. Every opening dumps heat the elements must replace.
- Switch off at the end rather than letting the thermostat hold an empty room.
Frequently asked questions
How much electricity does an electric sauna use per session?
A 6.8 kW heater running flat out through a 90-minute session uses at most 10.2 kWh. The thermostat cycling means real use comes in lower, so 10.2 kWh works as the planning ceiling.
Is an outdoor sauna expensive to run in the UK?
At the current capped rate of 26.32p per kWh, the ceiling works out at about £2.68 for a 90-minute session. Twice a week that stays under £25 a month even before thermostat cycling reduces it.
Does a sauna need its own electricity supply?
Yes. A 6.8 kW heater needs a dedicated circuit installed by a qualified electrician: 230 V single-phase with 1 × 35 A protection, or 400 V three-phase with 3 × 10 A. It is not a plug-in appliance.
Do these figures include the standing charge?
No, and that is deliberate. The standing charge applies to the property regardless of the sauna, so including it would overstate what the sauna itself adds to the bill.
Sources
- Ofgem: energy price cap unit rates, the 26.32p/kWh Direct Debit average for 1 October to 31 December 2026
- Harvia, manufacturer of the PC70 heater and its 6.8 kW rating
Next step
Running cost is the small line of the budget. The bigger ones sit in our full outdoor sauna cost guide, from the cabin itself to the base, the electrician and delivery. And when the numbers work, The Cabin Three electric shows exactly what the heater above lives in, with verified dimensions and the delivery process spelled out. The wider range sits in our outdoor sauna collection.