The extension lead across the lawn is where every garden office starts and where none should stay. A proper outbuilding supply is armoured cable, buried at depth, on its own protected circuit, often finishing at a small consumer unit in the building itself, and it's what turns a shed with a lead into a room that works all year. I run outbuilding supplies across Bristol, certified under my NICEIC registration and notified as new outdoor circuits require.
What a proper outbuilding supply involves
Steel-wire-armoured (SWA) cable sized for the building's real load, not just today's laptop, trenched at proper depth with marker tape, glanded correctly at both ends, RCD-protected, and finishing at either a connection unit or, for anything office-sized, its own small board so a fault in the garden trips the garden and not the house. The trench is the honest cost centre, which is why the quote asks how far the building is and what's between it and the house, and why open-trench moments are when everything else should go in too.
Garden offices: power, heating, data in one dig
An office needs more than power, and it all wants one trench: the supply for the desk and heating, plus a spare duct for a data cable, because garden Wi-Fi is a coin toss. It goes in together or gets dug twice. Inside, the spec that makes winter survivable: enough socket capacity, a properly sized heater circuit, lighting worth working under, and the outdoor lighting for the path back to the house, fed from the same supply while the ground is open.
Planning an office, shed or hot tub?
Send a photo of the garden and roughly where the building sits — I'll tell you the cable route and give you a written price.
Hot tub supplies
Hot tubs are the least forgiving load in the garden: water, people in it, and a heater drawing like a shower, which is why the supply spec is non-negotiable, a dedicated circuit, RCD protection, and a rotary isolator within sight of the tub so it can be cut off without a trip to the house. Tub suppliers publish their electrical requirements; send me the model's spec sheet with your enquiry and the quote comes back matched to it, not to a generic guess.
What an outbuilding supply costs
These are estimates, not quotes. Final costings always follow a free site inspection — and jobs often come in under the estimate, never over without you agreeing it first.
A typical garden office supply, trenched, SWA, small board in the building: £280–£460, with trench length the main mover and shared digs the main saver. Basic shed power: from £180. Hot tub circuits: £300–£500 to the supplier's spec. Indicative, confirmed from photos of the route and the distance.
How much does it cost to run power to a shed?
From £180 for lights-and-socket shed power on a short run, rising with distance and what's between here and there. The trench is most of the answer, so the route photos are most of the quote.
Can I use an extension lead to a garden office?
As a temporary bodge while the real supply is booked, people do. As the permanent arrangement for a heated room full of computer equipment, no, and every winter it runs is a season of finding out why.
What supply does a hot tub need?
Whatever its manufacturer specifies, typically a dedicated RCD-protected circuit with a local rotary isolator, and the spec sheet with your model's requirements turns my quote from a range into a number.
