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

A home sauna in the UK costs roughly 60p to £3 per session in electricity, or about £8 to £53 a month at two to four sessions a week. The variables that matter are heater size, cabin volume, insulation and session length — not the badge on the heater. At 26p per kWh, a small infrared cabin is cheap enough to be a rounding error on a household bill; an oversized, poorly insulated outdoor cabin is not.

Assumption used throughout this page: 26p per kWh including VAT. That is close to the Ofgem price cap unit rate for a direct debit customer in mid-2026, but the cap changes quarterly and varies by region, meter type and payment method. Check your own bill and scale the figures — every number here is linear in the unit rate, so at 30p per kWh you multiply by 1.15.

How to work out a sauna’s running cost

A session has two phases, and conflating them is why the numbers quoted by suppliers are so often wrong:

Phase 1 — warm-up. The heater runs at full rated power continuously until the cabin reaches temperature. Energy used = heater kW × warm-up hours.

Phase 2 — at temperature. The thermostat cuts in and the heater runs at a duty cycle, only working to replace heat lost through the walls, glass and ventilation. Energy used = heater kW × duty cycle × session hours.

The duty cycle is where insulation shows up. A well-insulated indoor cabin sits around 30–35%. An outdoor cabin in a British winter, or an uninsulated barrel, runs 45–60%. That is the single biggest lever on your bill, and it is decided when you buy the cabin, not afterwards.

Total kWh = (kW × warm-up hours) + (kW × duty cycle × session hours)

Worked examples

All three at 26p per kWh, with a single session per heat-up.

Infrared cabin, 4.5 kW, 2–3 person. Infrared heats the occupant rather than the air, so warm-up is short — around 15 minutes — and the panels then cycle at roughly 40% through a 40-minute session.

• Warm-up: 4.5 × 0.25 h = 1.13 kWh
• Session: 4.5 × 0.40 × 0.67 h = 1.21 kWh
• Total ≈ 2.3 kWh ≈ 60p

Note that 4.5 kW is a large full-spectrum cabin. Most two-person infrared units are 1.5–2 kW and run on a 13A socket, at roughly 25–30p a session. See infrared vs traditional for why the comparison is not like-for-like.

Traditional indoor sauna, 6 kW, ~6 m³, well insulated. Warm-up to 85°C takes around 40 minutes; duty cycle at temperature roughly 35% over a 45-minute session.

• Warm-up: 6 × 0.67 h = 4.0 kWh
• Session: 6 × 0.35 × 0.75 h = 1.58 kWh
• Total ≈ 5.6 kWh ≈ £1.45

Outdoor cabin, 8 kW, ~9–10 m³. Warm-up around an hour from a cold winter start; duty cycle around 45% over an hour.

• Warm-up: 8 × 1.0 h = 8.0 kWh
• Session: 8 × 0.45 × 1.0 h = 3.6 kWh
• Total ≈ 11.6 kWh ≈ £3.00

Monthly cost at 26p/kWh

Sauna	kWh per session	Per session	2/week	3/week	4/week
Infrared, 4.5 kW	2.3	£0.60	£5	£8	£10
Traditional indoor, 6 kW	5.6	£1.45	£13	£19	£25
Outdoor cabin, 8 kW	11.6	£3.00	£26	£39	£53
Outdoor cabin, 9 kW, uninsulated	~14	£3.65	£32	£47	£64

Indicative, at 4.33 weeks per month. Two people using the same heat-up costs the same as one — which is why household usage patterns matter more than the number of sessions logged. Our sauna cost calculator runs these numbers for a specific cabin and unit rate.

The levers, in order of how much they matter

1. Cabin volume. Energy scales almost directly with the air you are heating and the surface you are losing heat through. Doubling the internal volume roughly doubles both the heater size and the per-session cost, forever. A 4 m³ two-person cabin costs about half what an 8 m³ four-person cabin costs to run — and most households use two seats.

2. Insulation. 50–70 mm of mineral wool with a foil vapour barrier behind the lining is the standard build. A solid-stave barrel with no insulation typically pushes the duty cycle from ~35% to ~50% and lengthens warm-up by 30–50% in cold weather. Over three sessions a week that is easily £10–£15 a month on an outdoor cabin. The barrel vs cabin comparison covers the trade-off in full.

3. Glass area. Glazing looks superb and loses heat. Count each square metre of glass as roughly 1.2 m³ of extra cabin volume for heater sizing, and expect a matching increase in running cost. A glass door is worth it; a full glass front on an exposed north-facing cabin is a permanent tax.

4. Session discipline. Warm-up is the big block of energy, so two people in one heat-up costs what one person costs, and a second session an hour later — from a warm cabin — costs a fraction of the first. Batching sessions is the cheapest optimisation available.

5. Pre-heat scheduling. A timer or app control lets the cabin heat during off-peak hours on a time-of-use tariff. On a tariff with a cheap overnight rate, moving the 4–8 kWh warm-up block into the cheap window can cut the electricity cost of a session by half or more. It only works if you actually sauna at a predictable time; heating an empty cabin because the timer fired is pure waste.

6. Ventilation set correctly. Sauna vents are meant to be open in use — you need air exchange. But a cabin left with vents wide open between sessions, or a door left ajar, loses residual heat that would otherwise shorten the next warm-up.

Wood-fired: cheaper heat, not cheaper running

A wood-fired stove removes the electrical load entirely, which is genuinely attractive for a cabin at the bottom of the garden with no supply run — that trench is often the largest line item on an electrical quote.

The fuel, though, is not free. A session burns roughly 10–15 kg of kiln-dried hardwood. UK bulk prices in 2026 run about £0.35–£0.55 per kilo depending on whether you buy by the tonne, the dumpy bag or the net bag — so £3–£7 per session, which is at or above the 8 kW electric cabin. Add roughly 45–60 minutes of tending, an annual flue sweep, and the fact that most UK urban gardens sit in a smoke control area, where only a DEFRA-exempt appliance may be used. Wood-fired wins on atmosphere, off-grid capability and heat quality. It does not win on cost unless you have your own timber.

Against a gym or spa membership

Option	Typical UK monthly cost	Notes
Gym with sauna and steam	£40–£90	Plus travel and opening hours
Hotel or day spa passes, 2/month	£50–£120	£25–£60 per visit
Home 6 kW indoor sauna, 3/week	~£19 electricity	Plus purchase and install
Home 8 kW outdoor cabin, 3/week	~£39 electricity	Plus purchase and install

On running cost the home sauna wins comfortably. The honest comparison has to include the capital: a £6,000–£12,000 installed cabin against £600–£1,000 a year of gym membership puts the crossover somewhere between three and seven years for a regular user, before any value assigned to convenience or to no longer driving anywhere. Our home sauna cost page breaks down the purchase side, and are home saunas worth it works through the whole-of-life sum.

The most expensive mistake

Buying a cabin bigger than you will ever fill. An oversized sauna costs more to buy, needs a larger heater, often needs a heavier circuit, takes longer to warm up, and costs more every single session for the next fifteen years — to heat empty bench space. The marketing spec that says “6 person” is usually a count of people sitting bolt upright and touching; the same cabin is a comfortable three-person sauna. Size it for the sessions you will actually have, using our sizes and occupancy guide, and put the saved money into insulation instead.