Can I run a cable to my shed myself?

The reason this is not owner work is not the cable, which is straightforward, but the design. Voltage drop over distance, cable sizing, disconnection times, and above all the earthing arrangement for a separate building are genuine calculations, and getting the earthing wrong on an outbuilding is a specific and well-known hazard.

Safety

Step by step

1. Understand that it is a new circuit.A supply to a detached building is a new circuit originating at the consumer unit, and new circuits are notifiable under Part P in England and Wales, with equivalents in Scotland and Northern Ireland. It requires an Electrical Installation Certificate.
2. Know what cable is used.Steel wire armoured cable, buried at an adequate depth — commonly 450mm under a garden, deeper under a drive — with marker tape above it, or run overhead at a height that clears traffic with proper catenary support. Ordinary twin-and-earth in a duct is not an acceptable substitute.
3. Understand the earthing question.This is the part that matters most. Where the house supply is PME (also called TN-C-S), the supply earth may not be exportable to an outbuilding without additional measures, because of the risk if the network's neutral is lost. The electrician may need to install an earth electrode at the outbuilding and treat it as a TT installation. This is precisely why it is a design job.
4. Expect a small consumer unit in the outbuilding.A two-way or four-way board with a main switch and RCBOs, so the shed's lighting and sockets are separately protected and can be isolated locally. Not just a socket wired off the end of a cable.
5. Think about the load before it is designed.Light and a couple of sockets is one thing; a workshop with a table saw, a garden office with heating, or an EV charger on the same run is another. Say what you might want, because the cable size is decided once and upgrading it later means digging again.
6. Do the digging yourself if you want to save money.This is genuinely the biggest cost and most electricians will accept a trench dug to their specification. Agree the route and depth with them first, and never backfill until they have seen the cable and the warning tape in place.
7. Budget realistically.A basic shed supply — modest run, easy digging, small board at the far end — commonly falls in the region of £600 to £1,200. Long runs, hard ground, driveways to cross, an earth electrode, or a consumer unit change at the house end push it well above that. Get two or three quotes.
8. Get and keep the certificate.An Electrical Installation Certificate plus building control notification. When you sell, an uncertified outbuilding supply is exactly the sort of thing a buyer's surveyor flags.

Tips

• Lay a spare duct in the same trench while it is open, for data or for a future circuit. It costs almost nothing then and a fortune later.
• Photograph the cable route before backfilling, with measurements from fixed features. You will want that photograph the first time anyone plants a tree.
• If the shed only needs a light and a phone charger, solar with a battery is a legitimate alternative that involves no notifiable work at all.

Common mistakes

• Burying ordinary twin-and-earth in a plastic pipe — It is not designed for burial, the duct fills with water, and the cable has no mechanical protection. Spades go through it, and the cable is unprotected against damage in a way armoured cable is not.
• Running a permanent extension lead to the shed — It is unrated for the location, unprotected mechanically, and never inspected. It is also the arrangement most likely to be forgotten about and left running through a window all winter.
• Exporting the house earth to an outbuilding without assessment — On a PME supply, a lost network neutral can put the earth at a dangerous potential relative to true earth, which matters much more in a building where you are standing on ground. This is exactly why the earthing arrangement must be designed.

If it doesn't work

Questions people ask