Electric vs wood-fired sauna: what we check in a Gloucestershire garden

403.1 · The short answer

Electric is simpler to live with. Wood asks more of the site.

An electric heater needs a supply and nothing else: no flue, no fuel, no ash. It comes up to temperature on a switch or a timer and holds there on a thermostat. A wood-fired stove needs no electricity for its heat, but it brings a flue, clearances to every timber surface, a carbon monoxide alarm, somewhere dry to keep logs, and the question of smoke.

Neither is the better sauna. The deciding facts are usually about the house and the address, not the heater.

403.2 · Power

What an electric heater asks of the house

A sauna heater is one of the largest loads a house will carry. The current it draws is its rating divided by the voltage: at 230 volts, a 6 kW heater draws about 26 amps and a 9 kW heater about 39. That is why it runs on its own circuit from the consumer unit, never from a socket.

The circuit is only half of it. The electrician also adds up what the whole house can draw at once and sets it against the main fuse. An electric shower, a heat pump, an induction hob and a car charger all count. Where the supply is tight, a load management device or an upgrade from the network operator may be needed, and an upgrade takes time to arrange.

1. The heater's rating, sized to the volume of the room and how much of it is glass.
2. A dedicated circuit, with the cable sized for its length.
3. The house's maximum demand against its main fuse.
4. The cable route from the house to the sauna, trenched before the base goes down.
5. Certification under Part P by a registered electrician.

Most homes have a single-phase supply, and some larger heaters are made for three-phase. So the heater is chosen to suit the supply, not the other way round.

403.3 · The flue

What a wood-fired stove asks of the sauna

A wood-burning sauna stove sits inside a timber room. The stove maker sets the minimum clearances to anything combustible, and in a sauna that means the walls, the benches and the ceiling. The flue passes through the roof in an insulated section and rises clear of it, to a height set by Approved Document J and the maker's instructions.

The stove should be fitted by a HETAS-registered installer, who can certify the work, and a carbon monoxide alarm goes in with it. Some stoves are fed from inside the hot room and some through the wall from outside, which keeps ash and logs out of the sauna. The choice changes the plan of the building, so it is made before the drawings are.

Logs need a dry, ventilated store: close enough to the sauna to carry in the dark, far enough from the stove to keep its clearances.

Sheet 407: the stove, the flue and the log store, in order→

403.4 · Smoke

Smoke control, the neighbours and the flue's height

Parts of Cheltenham and Gloucester are smoke control areas. Wood is not an authorised fuel, so in a smoke control area it may only be burned on a DEFRA-exempt appliance. Gloucester City Council's page says it is recommended that the whole city be made a smoke control area. Stroud says it has none, as did the Forest of Dean in 2023, and we found nothing either way from Tewkesbury or Cotswold. GOV.UK's advice is to ask the council. We check a Cheltenham address on the council's map, and confirm any other with its council, before a wood-fired design goes any further.

Inside or outside a smoke control area, smoke can become a statutory nuisance under the Environmental Protection Act if it keeps drifting into a neighbour's garden or windows. Where the flue sits against the boundary, the survey looks at the prevailing wind and the house next door.

The height limits in permitted development apply to the sauna, not its flue. Within 2 metres of a boundary the sauna itself may be 2.5 metres high, and the flue rising above it is not counted. Where you want the position confirmed in writing for your garden, a Lawful Development Certificate from the council does that.

Planning permission for a garden sauna in Gloucestershire→

403.5 · Heat and cost

Heat-up time and running cost

An electric heater is switched on, often from a phone or a timer, and left. A wood-fired stove is lit, fed and watched, and the heat builds as the stones and the room take it up. For both, a cold January evening takes longer than a mild one, and a glass front loses heat faster than a solid wall. One maker's figure for an electric heater: HUUM's manual for its DROP, the heater in our barrel photographs, says that in a properly insulated room with a heater of the right capacity it takes around one hour to reach the desired temperature.

The two are paid for differently. Electric is metered: a heater can use at most its rating for each hour it runs flat out, so an 8 kW heater uses up to 8 kWh an hour while heating, then less as the thermostat cycles. Multiply by the unit rate on your bill. Wood is bought by the load and stored.

A worked example. Ofgem's price cap for 1 October to 31 December 2026 sets the Great Britain average electricity unit rate by Direct Debit at 26.32p a kWh, with no VAT on electricity from 1 October 2026 to 31 March 2027 (read on 26 October 2026). At that rate an 8 kW heater costs at most about £2.11 for each hour it runs flat out, and less once the room is up to heat. Your own tariff and region will move the figure, and the cap changes every three months.

Work out your own: the running-cost calculator, sheet 406→

In England, wood sold for burning at home in amounts under 2 cubic metres must be certified Ready to Burn, which means a moisture content of 20 per cent or less. Loads of 2 cubic metres or more must come with a notice on drying and storing it yourself, and a stove burns wet wood badly and smokily.

403.6 · The feel

What each one is like to use

On either heater, water ladled onto hot stones gives the burst of steam the Finns call löyly. The difference is everything around it. Wood brings the sound and smell of a fire, a glow through the stove door and the business of lighting it. Electric is quiet, even, and ready when you are.

If the sauna is for half an hour most evenings after work, a heater that is ready on a timer counts for a lot. If it is for a long evening at the weekend, lighting the fire is part of the evening. Most gardens can take either. Some can only take one, and the survey says which.

403.7 · Start from either

Choose a heater, or choose not yet

The configurator asks for electric, wood-fired or not sure, and the notes that come back with the design change with the answer. The site survey then confirms the supply, the flue and the address before anything is ordered.

Start a design→

The two heaters, on our services page→

Next: charred larch, cedar or thermowood→

403.8 · Questions

Questions people ask about sauna heaters