Sauna electrical requirements UK: supply, Part P and what an electrician costs

Plug-in or hard-wired?

Type	Typical power	Supply	Example (retailer’s own wording)
Small infrared cabin	about 1.2–2kW	Some run from a standard 13A socket	Steam & Oak Kajo 2: “standard 13A plug — no electrician”
Larger infrared cabin	2–3.5kW	Often a dedicated circuit. Check the listing	Check each listing
4.5kW traditional heater	4.5kW	Dedicated hard-wired circuit	SaunaPlunge Brontë: “a dedicated 20 A hard-wired electrical supply”
6kW traditional heater	6kW	Dedicated 32A circuit	Polar Recovery Sauna Cube: “a dedicated 32AMP electrical supply” plus an isolator or 32A commando socket; Steam & Oak Prism: “dedicated 32A single-phase supply”; CenturaHeat 4-person: 32A
9kW traditional heater	9kW	Heavy single-phase or three-phase	Holl’s Orphée: “typically 400V three-phase or a heavy single-phase circuit”

As a rough guide, current = power ÷ voltage: 4.5kW ÷ 230V ≈ 20A, 6kW ≈ 26A, 9kW ≈ 39A. That’s why bigger heaters need dedicated circuits and why a 9kW heater can be a problem for some homes.

What the heater manufacturer specifies

Heater manuals set out the cable and fuse sizes. For example, Harvia’s manual for its Cilindro heaters gives:

Heater	Single phase (230V)	Three phase (400V)
6.8kW (PC70)	3 × 6mm² cable, 35A fuse	5 × 1.5mm² cable, 3 × 10A fuses
9.0kW (PC90)	3 × 10mm² cable, 40A fuse	5 × 2.5mm² cable, 3 × 16A fuses

The manual also says the connecting cable must be rubber type H07RN-F or equivalent, and that PVC-insulated cable is forbidden because heat makes it brittle. Your electrician will work from the manual for your actual heater.

The rules in England

Part P: it’s notifiable

Approved Document P says these jobs are notifiable:

• installing a new circuit;
• replacing a consumer unit;
• any addition or alteration to existing circuits in a special location, which includes “a room containing a swimming pool or sauna heater”.

A garden sauna on its own circuit is notifiable. The easiest route is an electrician registered with a competent person scheme (such as NICEIC or NAPIT), who can self-certify the work and notify building control for you. You should get an Electrical Installation Certificate, and later a Building Regulations compliance certificate.

BS 7671 Section 703

The IET Wiring Regulations (BS 7671) have a section for “rooms and cabins containing sauna heaters” (Section 703). It covers things like where equipment can be fitted and what protection is needed. Your electrician will know it. As a buyer, the point is that sauna wiring isn’t like adding a socket.

Wales has its own Part P rules. Scotland and Northern Ireland have separate building regulations. Check locally.

Running power to a garden sauna

For an outdoor sauna, the electrician will usually run armoured (SWA) cable from your consumer unit to the sauna, often buried. M62 Electrical’s guide says it should be buried at about 600mm under a lawn. Depending on your supply and earthing arrangement, you may need an earth rod (a TT system) at the outbuilding.

Typical costs

Item	Typical cost	Source
Supply up to 15m from the house	£700–£1,100	M62 Electrical, 2026
Supply 15–30m	£1,200–£2,000	M62 Electrical, 2026
Trenching	£300–£700 extra	M62 Electrical, 2026
Earth rod / TT system, if needed	£250–£450	M62 Electrical, 2026
6mm² SWA cable	about £4.10 per metre	BuildWiz
10mm² SWA cable	about £6.90 per metre	BuildWiz
Electrician day rate	about £500 (about £55 an hour)	Checkatrade, 2026

These are third-party price guides, not quotes. Your price depends on distance, ground conditions and whether your consumer unit has space and capacity. Use the sauna cost calculator to add your quote to the total, and see the garden sauna cost guide for everything else.

Questions to ask before you buy

1. What heater, at what kW, and what supply does the retailer specify? Get it in writing.
2. Does my consumer unit have a spare way and enough capacity? If not, a new consumer unit adds cost.
3. Is my main supply big enough? Ask the electrician to check before you commit to a 9kW heater.
4. How far is the sauna from the consumer unit, and what’s in the way? Patios and driveways make trenching more expensive.
5. Will the electrician notify the work under Part P and give me certificates?
6. Does the retailer’s installation include the electrics? Usually it doesn’t: assembly teams build the sauna and your electrician connects it.