Show the formula and working
This sauna running cost calculator works out what a home sauna costs per session and per year in electricity. Enter the heater power in kW, how long the sauna takes to heat up, how long you use it, how much of that time the heater is running and how many sessions you have a week. It starts with the UK price cap unit rate, has EU presets, and you can type your own tariff.
Quick answer: A home sauna costs its heater power in kW times the hours it is heating times your unit rate. A 6 kW sauna that heats up for 45 minutes and then runs half the time during a 60 minute session uses about 7.5 kWh, which costs about £1.97 a session at 26.32p. Twice a week, that is about £205.30 a year.
How Is Sauna Running Cost Calculated?
The cost has two parts: the heat up, when the heater runs at full power, and the session, when the thermostat switches the heater on and off to hold the temperature.
During the heat up, the calculator multiplies the heater power by the heat up time. During the session, it multiplies the power by the session time and by the share of time the heater is running, because the thermostat cycles once the room is hot. The total kWh for one session times your unit rate gives the cost per session. Multiplied by your sessions a week and 52 weeks, that gives the yearly cost.
The heating share and heat up time depend on the size of the cabin, how well it is insulated, the starting temperature and your target temperature. An outdoor sauna in winter will take longer to heat than an indoor one in summer.
How Do You Use the Sauna Calculator?
- Enter the sauna heater power from its plate.
- Enter how long the sauna takes to heat up.
- Enter the session length and the share of it the heater runs.
- Enter how many sessions you have a week.
- Choose a price preset or enter your unit rate.
How Much Does a Home Sauna Cost to Run?
At 26.32p per kWh, a home sauna typically costs around £1 to £3 a session, depending mostly on heater size and heat up time.
| Heater power | Energy per session | Cost per session | Cost per year (2 a week) |
|---|---|---|---|
| 3 kW | 3.75 kWh | £0.99 | £102.65 |
| 4.5 kW | 5.63 kWh | £1.48 | £153.97 |
| 6 kW | 7.5 kWh | £1.97 | £205.30 |
| 8 kW | 10 kWh | £2.63 | £273.73 |
The heater power is printed on the heater’s rating plate. The 26.32p unit rate is the Ofgem price cap average for October to December 2026. You can check the latest figure on the Ofgem energy price cap page.
What About Infrared Saunas?
Infrared saunas usually have lower powered heaters, often a few kW or less, and many warm up faster, so they tend to cost less per session.
The calculation is the same: enter the total power of the infrared panels, the warm up time and the session time. Because infrared panels warm you more directly than the air, some run for a larger share of the session, so use a higher heating share if your sauna’s controls show that the panels stay on.
Does Heat Up Time Matter?
Yes. In the default example, the heat up is about 60% of the energy used per session.
That is why a well insulated cabin, a tight door and a sensible target temperature make a big difference. Heating the sauna only as long as needed, and starting the session as soon as it is ready, saves more than shortening the session itself. If you also have a hot tub, the hot tub running cost calculator works out its cost in the same way.
Worked Example: A 4.5 kW Sauna Three Times a Week
Example: a household uses a 4.5 kW indoor sauna three times a week. It heats up in 40 minutes, sessions last 45 minutes, and the heater runs about half that time. The unit rate is 26.32p.
- Heat up: 4.5 kW x 40 minutes = 3 kWh, about 79p
- Session: 4.5 kW x 45 minutes x 50% = 1.69 kWh, about 44p
- Per session: 4.69 kWh, about £1.23
- Per year: 156 sessions x £1.23 = £192.47
Using the sauna three times a week costs about £3.70 a week in this example. If you have a time of use tariff or solar panels, heating the sauna in cheap or sunny hours can cut this a lot.
Tips to Cut Sauna Running Costs
Most savings come from shorter heat up and less heat loss.
- Keep the door closed during heat up and sessions.
- Set a sensible target temperature rather than the maximum.
- Check door seals and cabin insulation, especially in outdoor saunas.
- Plan sessions back to back for the household, so you heat up once.
- Use a timer or app to start heating just before you need it.
- Run it in cheap hours if your tariff has them.
A sauna heater draws a large current, so it needs its own correctly sized circuit, installed by a qualified electrician.
Sauna Running Cost FAQs
How much does a sauna cost per session?
A 6 kW sauna with a 45 minute heat up and a 60 minute session costs about £1.97 at 26.32p. Smaller heaters and shorter heat up times cost less.
How much electricity does a home sauna use?
A typical session uses several kWh, mostly during heat up. A 6 kW heater uses 6 kWh for each hour it runs at full power.
Are infrared saunas cheaper to run?
They often use lower powered heaters and warm up faster, so they usually cost less per session. Enter your panel power to check.
Does the sauna heater run the whole session?
No. Once the room is hot, the thermostat switches the heater on and off. The share of time it runs depends on insulation and the target temperature.
Is an outdoor sauna more expensive to run?
It can be, especially in winter, because it starts colder and loses more heat. Good insulation and door seals help.
Can I run a sauna on a normal plug?
Most traditional sauna heaters need a dedicated circuit. Some small infrared units plug in. Always follow the maker’s installation instructions.
Checked October 2026. Sources: Ofgem energy price cap. Heat up times and heating share are examples; use your sauna’s figures.