Can I plug an outdoor patio heater into a standard extension lead?

No. Standard indoor extension leads are not weatherproof and are dangerous outdoors. Even a heater on a covered patio in damp UK conditions will expose an unrated extension to moisture. The correct approach is to have a properly installed outdoor socket with an IP65 rating, mounted on a weatherproof surface box, supplied via a circuit with 30 mA RCD protection. An outdoor socket can be added as a fused spur from the ring final or as a dedicated circuit, depending on the heater's power rating.

Does an outdoor circuit need an RCD?

Yes. BS 7671 regulation 411.3.3 requires that all socket outlets rated up to 20 A that may reasonably be expected to supply portable equipment outdoors are protected by a 30 mA RCD. In a domestic property, this means all outdoor sockets must be on a 30 mA RCD-protected circuit. Amendment 2 to the 18th Edition (2022) extended RCD protection requirements to cover all circuits in domestic premises, so a hardwired outdoor heater on its own dedicated circuit also requires 30 mA RCD protection.

What IP rating do I need for outdoor sockets and accessories?

For outdoor positions, BS 7671 and the accessory manufacturer's installation instructions define the minimum IP rating. IP44 (protection against splashing water in any direction) is the minimum for most covered outdoor positions. IP65 (protection against directed jets of water) is required for exposed positions where the accessory could be wetted directly by rain or a hosepipe. Always check the accessory's IP rating is appropriate for where it will actually be mounted -- a socket under a deep overhang may be fine with IP44, while one on an open fence post needs IP65.

Is wiring an outdoor socket or patio heater supply notifiable under Part P?

Yes. Installing a new circuit outdoors is notifiable work under Part P of the Building Regulations in England. It must be carried out by a registered competent person (such as an NICEIC or NAPIT-registered electrician) or notified to your local Building Control before work begins. Adding an outdoor socket as a spur from an existing ring final is notifiable if it involves a new circuit, but minor works such as replacing an existing outdoor socket like for like are not notifiable. If in doubt, use a registered electrician who can self-certify the work.

How to Wire an Outdoor Electric Patio Heater (UK)

Helpful video reference. This installation guide from Electric Radiators Direct, a UK electric heating retailer, covers the installation considerations for an outdoor electric heater, including mounting options and supply requirements. Worth watching to understand the practical steps before starting your own installation.

Before you start. Any new outdoor circuit is notifiable work under Part P of the Building Regulations. In England, either use a registered competent person or notify your local Building Control before starting. Never work inside a live consumer unit, and always confirm the supply is dead at the accessory with a voltage tester before touching any conductor.

1. Check the heater's electrical specification and IP rating

Read the manufacturer's data sheet before buying any accessories or cable. Note the rated power in watts or kilowatts, the supply type (plug-in or hardwired), and the IP rating of the heater body itself.

Most domestic patio heaters are between 1.5 kW and 3 kW, drawing up to 13 A at 230 V. This puts them within the capacity of a 13 A socket supplied from the ring final. Larger commercial-grade units may need a dedicated circuit. Check the data sheet -- the manufacturer will specify.

The heater's IP rating tells you how weatherproof the unit itself is, but it does not govern what the accessories and cable supply need to be. Those are determined by their mounting position in the open air.

2. Plan the cable route and protection method

There are three common routes for an outdoor patio heater supply:

Surface-run on the house wall: Cable clipped to the wall in UV-resistant conduit or trunking, running from an indoor socket or consumer unit to an outdoor accessory. This is the most straightforward route. The conduit protects the cable from mechanical damage and UV degradation.

Through the wall: Short section from an indoor accessory through the cavity or solid wall to an outdoor back box. The hole must be sleeved and sealed against damp penetration -- drill at a slight downward angle toward the outside so water cannot track in.

Underground: Where the cable must cross a patio or lawn, it must either be armoured cable (SWA) buried at a minimum depth of 500 mm, or an unarmoured cable drawn through rigid conduit buried at the same depth. Mark the route and record it so the cable is not damaged later by digging.

3. Fit a 30 mA RCD-protected circuit or fused spur

BS 7671 regulation 411.3.3 requires 30 mA RCD protection for all outdoor socket outlets. Amendment 2 to the 18th Edition (2022) extended this requirement to all domestic circuits, so a hardwired outdoor supply also requires 30 mA RCD protection.

If the heater is plug-in and the outdoor socket will be fed from the ring final, the simplest solution is a fused spur with a 13 A fuse, supplied from an existing ring circuit protected by a 30 mA RCD at the consumer unit. If your consumer unit has a main RCD covering all circuits, the outdoor spur is already protected. If not, fit a local 30 mA RCD socket or FCU with built-in RCD.

If the heater is hardwired and draws more than 13 A, fit a dedicated RCBO at the consumer unit sized to the heater's rated current.

4. Install IP65-rated outdoor accessories

Every accessory mounted outdoors -- the socket, FCU, or switched spur -- must be rated for outdoor use. For fully exposed positions, IP65 is the appropriate rating. For positions under a deep overhang where the accessory will never be wetted directly, IP44 may be sufficient, but IP65 is the better choice for all outdoor use.

Use a weatherproof surface back box (the kind with a sealing gasket around the faceplate) rather than a standard dry-lining box. Cable entry points on outdoor back boxes must be sealed -- use the gland fittings supplied with the surface box, or IP-rated cable glands if the entry is from conduit.

Tighten all cover screws evenly so the gasket seats fully. A partially tightened outdoor socket loses its IP rating and will allow moisture in.

5. Run and terminate the cable

For a surface run in conduit on the building fabric: use 2.5 mm2 twin-and-earth in UV-stabilised round conduit. Clip the conduit at 500 mm intervals. At the building penetration point, seal around the conduit with an appropriate mastic or expanding foam.

For an underground run in SWA: strip the outer sheath carefully with an armoured cable stripper, not a knife, to avoid nicking the wire armour. Terminate the armour in an SWA cable gland that provides both mechanical grip and an earth connection via the gland body. The armour must be earthed at both ends.

At the accessory, strip only the length of insulation that fits the terminal -- typically 10 mm. Do not leave bare conductor visible beyond the terminal. Tighten screw terminals firmly; finger-tight is not sufficient for outdoor accessories that may experience thermal cycling.

6. Make the final connection to the heater

If the heater is plug-in: install the outdoor socket, restore power, and use an RCD tester to confirm the protective device trips at 30 mA before plugging in the heater. Then plug in and test.

If the heater is hardwired: the final connection point is usually inside the heater's wiring compartment, accessed via a removable cover. Follow the manufacturer's wiring diagram. Connect brown to L, blue to N, and green-and-yellow to the earth terminal. Replace the cover and all weather seals. The heater should have a local isolator -- a switched FCU or a double-pole isolator on the wall -- so it can be de-energised without going to the consumer unit.

7. Test and record the installation

Carry out the required inspections and tests under BS 7671 Chapter 61 before leaving the job: insulation resistance, polarity, earth continuity, and RCD operating time. For a new circuit, issue a Minor Electrical Installation Works Certificate (if adding a spur to an existing circuit) or an Electrical Installation Certificate (if adding a new circuit from the consumer unit).

If you are a homeowner carrying out your own work: notify Building Control before you start, not after. Their inspector will want to see the installation before it is concealed (underground sections especially) and again on completion.

Stop and call a registered electrician if: the consumer unit has no space for an additional way, the existing main fuse or meter tails appear undersized, the cable route requires crossing a neighbour's property or a public footpath, the outdoor supply is for a building separate from the house (a detached garage, garden office, or outbuilding -- these have additional requirements), or the heater is supplied at more than 230 V single-phase.

When to call us

Richard supplies and certifies outdoor circuits for patio heaters, garden offices, outbuildings, and EV chargers across Sandwich and east Kent. If the job involves a new consumer unit way or underground cable, he can price the full scope at once.

Outdoor electrical supply in Sandwich or east Kent?

Richard installs outdoor sockets, RCD-protected circuits, and armoured cable runs for patio heaters, garden lighting, and outbuildings. All work certified.

Contact Richard

How to wire an outdoor electric patio heater