Sauna heaters: kW, room size, supply and price

Only 29% of the garden saunas in our dataset come with a heater, so for most buyers this is a second purchase, and it’s easy to get wrong. Too small and the room never gets properly hot; too big and you pay for a circuit and a heater you don’t need. This page lists 74 heater listings from 6 UK retailers, with the output, room size, supply and price each one states, and a link to our heater size calculator to size yours.

How to size your heater

The rule most makers use comes from HUUM: allow about 1 kW of heater output for each “calculated” cubic metre. Take the volume of the hot room, inside measurements, then add 1 m³ for every square metre of glass or bare log wall, because those lose heat faster than an insulated wall. A 2 m × 1.8 m × 2 m room with a solid door is 7.2 m³, so about a 7 kW heater; give it a fully glazed front and it needs 10 kW or more.

Our sauna heater size calculator does the sum for a cabin, cube or barrel, adds the glass, and lists every heater in our data whose maker says it suits that room, cheapest first. Treat the result as a starting point and let the maker’s stated room range (the “Room size” column below) decide between two sizes.

Source: HUUM: Sauna Heater Size Calculator. Checked 30 September 2026.

Every sauna heater listed

Prices as shown on each retailer's page on 30 September 2026. Room sizes and supply are the retailer's stated figures. Aqualine Saunas and Leisurequip do not say whether their prices include VAT; Leisurequip shows “from” prices only, so some rows have no price.

How many kW do you need?

Heater makers state a range of room sizes for each output. Across the listings above, this is what they say:

For most garden saunas that means:

• Two-seat barrels and small cabins (3 m³ to 6 m³): a 4.5 kW heater.
• Four-seat barrels and cubes (5 m³ to 9 m³): 6 kW to 8 kW.
• Six-seat barrels and larger cabins (8 m³ to 14 m³): 9 kW, more with a glass wall.
• Big cabins and glass-fronted rooms: 10.5 kW and up. A 10.5 kW heater still runs on single phase but needs a 50 A circuit; 12 kW and up is often three-phase only.

Barrels hold less air than a square room of the same length, so they often sit at the lower end. Our barrel saunas and cabin saunas pages show which heater each model comes with, where it’s included.

Electric supply: single phase or three phase?

A sauna heater is one of the biggest loads you can put on a home’s supply. A standard 13 A socket delivers about 3 kW, so almost every sauna heater needs its own circuit from the consumer unit, installed by an electrician. Here’s what the retailers state for heaters where they give both the single-phase and three-phase figures:

Supply requirements as stated on the retailer's product page. Your electrician will size the cable and protection for your installation; these figures show why a sauna heater needs its own circuit.

Most UK homes have a single-phase supply. The bigger heaters (12 kW and up in the HUUM HIVE range) are three-phase only, which rules them out for most gardens unless you already have a three-phase supply. Our electrical supply calculator works out the current for any heater size on either supply.

Installing a new circuit is notifiable work under Part P, and a room containing a sauna heater is a Part P special location, where any addition or alteration to a circuit is notifiable. Our guide to installing a garden sauna explains what that means for you.

Sources: IET: Part P (England and Wales) - Frequently asked questions. Checked 30 September 2026.

Controls: built-in, separate controller or Wi-Fi

How you switch the heater on and set the temperature varies:

• Built-in controls: dials on the heater itself. Simplest and cheapest, but you set it inside the hot room. 6 listings.
• Separate controller: a wall-mounted panel, usually outside the hot room. Many heaters need one and it’s often sold separately, so check it’s in the price. 30 listings.
• Wi-Fi app: a controller you can use from your phone, so the sauna is hot when you get to it. 5 listings.

Electric heaters are either continuously heated, the most common type, or heat-storing.

Sources: Finnish Sauna Society: Sauna heater. Checked 30 September 2026.

Stones

Sauna stones sit in or on the heater and store the heat that makes steam when you throw water on them. The quantity depends on the heater’s output and design: from a few dozen kilos to several hundred. In our data, the HUUM DROP holds about 55 kg, the HIVE Mini 150 kg and the full-size HIVE 250 kg. Some listings include stones; many don’t, so add them to the price if you need them.

Sources: Finnish Sauna Society: Sauna heater. Checked 30 September 2026.

Wood-burning sauna stoves

Wood stoves need no electrical supply at all, but they come with a flue and, in many towns, smoke control rules. We list 15 wood stove listings in the table above; see wood-burning sauna stoves for them on their own, plus the rules on smoke and fitting.

Harvia vs HUUM

Harvia (from Finland) and HUUM (from Estonia) are the two names you’ll see most on UK heater listings: 69 of the 74 in our data.

Harvia has the wider range, including the cheapest heaters in our data (the Vega and KIP). HUUM’s range goes up to 250 kg of stones in the full-size HIVE, and most of its heaters need a separate controller. Compare every model on Harvia heaters and HUUM heaters.

Same heater, different price

The same heater can cost very different amounts depending on where you buy it, partly because some prices include stones or a controller and some don’t.

Grouped by brand, range and stated output. Each price is labelled with what the retailer says it includes; compare like with like, and add the cost of a controller and stones where they're not included.

What each size costs to run

A bigger heater uses more electricity, but it also heats the room faster. At the Ofgem cap of 26.32p per kWh, and on our stated assumptions, here’s the cost per session:

Change the assumptions in the running cost calculator. For the heater’s place in the total budget, see how much a garden sauna costs.