Garden Rooms and Hot Tubs in London: The Electrics You Need

Garden rooms, home offices at the end of the garden and hot tubs are popular in London homes with outdoor space. They all need a safe power supply run from the house, and that is where many problems start: extension leads through a window, cables lying on the lawn, or a hot tub plugged into an outdoor socket that was never meant for it. This guide explains what a proper installation looks like. It is general information, not legal advice.

Why a dedicated supply matters

A garden room with heating, lighting, sockets and a computer can draw as much power as a small flat. A hot tub heater draws a lot of power for hours at a time. Both usually need their own circuit from the consumer unit, sized for the load and the length of the cable run, rather than a spur from an existing socket.

Running the cable to the garden

• Cables run underground should be a suitable armoured type, buried at a safe depth or protected along fences and walls.
• The route should be recorded so nobody digs through it later.
• Cables should not be left on the surface or clipped loosely along fences where they can be damaged.
• The cable size depends on the load and distance; a long run needs a larger cable to avoid voltage drop.

Inside the garden room

Most garden rooms need a small consumer unit of their own, with RCD protection for the sockets and lighting. Plan sockets for a desk, heater and any gym or music equipment, and outdoor lighting for the path back to the house. See our guide to garden and outdoor sockets.

Hot tubs and swim spas

Hot tubs combine water, electricity and people, so the rules are strict. Most need a dedicated circuit with RCD protection and a local isolator that can be reached from outside the tub but not from inside it. Always follow the maker's installation instructions for the supply needed. Plug-in inflatable tubs should be used only with a suitable outdoor socket, never through an extension lead.

Certificates and Building Regulations

Adding a new circuit, and electrical work in outdoor and wet locations, is usually notifiable under Building Regulations in England. A registered electrician can certify the work and notify it for you, and you should keep the Electrical Installation Certificate with your house papers. It will matter when you sell.

Check the house can take the extra load

Before adding a garden room or hot tub, an electrician should check your main fuse, consumer unit and earthing. If you also plan an EV charger or heat pump, plan all the loads together. If your RCD trips when the tub heats up, see our guide on why an RCD keeps tripping.

Book a survey

Energy North Ltd wires garden rooms and hot tubs across North, East and West London with City & Guilds certified electricians. See our website to book a visit.