Cost guide
How much do outbuilding supplies cost?
A submain and a small board is £400 to £1,200 on a straightforward run. Under a drive or across hard landscaping it runs £900 to £2,200, almost all of it groundwork.
Typical prices
Ranges, not quotes. A quote depends on your room.
| Work | Typical UK price |
|---|---|
| Submain and small board, 15m across soft ground | £400 to £800 |
| Submain and small board, 25m with a path crossing | £700 to £1,200 |
| Submain under a block drive or concrete | £900 to £2,200 |
| Lighting and sockets fitted in the outbuilding | £250 to £600 |
| Upsizing the submain for a future EV charger | £80 to £250 extra |
| Earth rod and arrangement at the outbuilding | £120 to £250 |
Oversize the cable. It is the one part of this job that cannot be changed without digging the trench again, and the extra cost of going up a size now is a fraction of what the second trench costs.
What moves the price
- Trench length and what it crosses. Lawn, border, path, block drive and concrete are five different prices.
- Cable size, which follows what the building will hold rather than what is in it today.
- Whether the house consumer unit has a spare way of the right rating.
- Earthing at the outbuilding, and whether a rod and a separate arrangement are needed.
- How many circuits go in at the far end: lighting, sockets, a charger, machinery.
- Reinstatement, and whether turf, paving or tarmac has to be put back.
Who quotes for it
Questions about outbuilding supplies
Can I add an EV charger later?
Only comfortably if the submain was sized for it. Upgrading the cable means opening the trench a second time, so the cheap decision is to oversize now.
Does the garage need its own consumer unit?
For anything beyond one circuit, yes, and it is the point of doing it properly: local protection, room to add circuits, and a fault out there that does not take the house with it.