A garage, loft or outbuilding needs a supply designed for distance, planned loads and future use. A qualified Swansea electrician can specify safe cabling, protection, earthing and certification. This can cover lights, sockets, heating, workshop equipment or EV charging.
Choose a supply that matches your space
Choose the supply around the finished use, not today’s minimum needs. A submain can feed one circuit or a small consumer unit with several circuits.
| Space and use | Likely arrangement | Typical scope | Indicative Swansea cost |
|---|
| Loft storage with lights | Existing circuit extension or new circuit | Loft lighting, switch and safe access | £450 to £1,200 |
| Garage with sockets and door | SWA supply, often a small consumer unit | Lighting, sockets, door feed and isolation | £800 to £2,500 |
| Garden office with heating | Dedicated SWA submain and consumer unit | Power, data route, heating allowance and test work | £1,500 to £3,500 |
Detached garages, sheds and garden offices often need armoured SWA cable. The cable must be correctly sized and routed. It may need burial and suitable glands.
A permanent extension lead cannot replace a protected, tested fixed supply.
A garage or outbuilding often benefits from its own consumer unit. This applies when it has separate light and socket circuits, heating, tools, a utility area or EV provision.
RCBO protection can stop one faulty circuit from cutting power to every circuit.
A comparable quote should separate fixed design and test work from variable costs, as these affect the final price.
For a garage electrical supply, route length often causes the biggest price difference. Cable size also matters, as does the route through the house or outside.
Buried cable may cross grass, paving or a driveway. A short surface route for lights may need modest materials. A longer route may need voltage-drop limits, a garage consumer unit, RCBO protection and reinstatement work.
Request a stated cable type and size. Ask for a route drawing, excavation allowance, consumer-unit specification and test-certification cost. This helps reveal essential work missing from a cheaper quote.
Size cable for load, route and future plans
Cable size depends on expected load, route, protective device and voltage drop. Distance alone does not set the cable size.
A cable for lights may not safely support heaters, welders, machinery or an EV charger.
Trenching can be the costly part. Buried SWA needs a safe route and protection from future digging. Paving, gardens or driveways may also need repair.
Ask whether groundworks and surface repairs are included.
Heating and EV charging raise demand
Electric heaters, kettles, workshop machinery and EV chargers can draw far more power than lights and phone chargers. EV charging needs a dedicated design and protective measures.
The electrician must also check whether the house supply has enough capacity.
For most Swansea garage and outbuilding projects, specify the highest realistic future load before choosing cable. A 15-metre run for lights and two sockets may be straightforward. The same route may need a different design for heating, workshop machinery or EV charging. Pay for a load assessment and clear cable specification first. Replacing buried cable later is usually the costly part.
Work packages help match the installation to the intended use. A basic loft package may include a dedicated loft lighting circuit and two-way switching. It can also include safe cable routes and agreed alarm wiring.
A workshop package can separate lighting and socket circuits. It should allow for a compressor, welder or fixed machinery. Do not rely on one general-purpose circuit.
Garden office electrics can allow for sockets, lights, broadband routes and electric heating. An EV charger supply needs a dedicated circuit. Check the dwelling’s incoming capacity first.
For detached outbuilding power, specify isolation, earthing arrangements and SWA armoured cable. State the required number of circuits from the outset.
Check Welsh approvals before conversion work
Planning permission, Building Control approval and electrical certification are separate checks. A loft or garage conversion may involve all three. Confirm the project’s needs with Swansea Council before work begins.
Lofts may need alarm upgrades
A loft conversion may need new circuits and upgraded smoke alarms. This forms part of the wider fire-safety design.
Plan alarms, cabling, insulation protection and maintenance access before ceilings are closed.
Planning is not Building Control
Planning concerns what may be built or changed. Building Control checks how safely work is completed.
Confirm Part P notification routes in Wales. Ask which certificate or notification the electrician will provide.
For a Swansea conversion, treat planning, Building Control and electrical notification as separate questions. Planning permission may be needed for external changes, a change of use or local restrictions.
Some loft and garage work may fall within permitted development. This depends on the property and proposal.
Building Control often matters when a garage or loft becomes habitable accommodation. It considers structure, insulation, ventilation, fire escape and stairs alongside the electrics.
Part P covers electrical safety in Welsh dwellings. Ask if the electrician can use a competent-person notification route. Otherwise, Building Control may need notice before work starts.
Keep approval documents and the electrical certificate with property records.
Avoid cheap shortcuts and unclear quotes
Ask for an itemised design, not just “a cable to the garage”. It should state the SWA route, load allowance, earthing and isolation. It should also state protective devices, testing and certification.
Compare contractors’ registration, insurance and relevant garage, loft or outbuilding experience.
Earthing cannot be guessed
Earthing and bonding must be checked at the house before connecting a detached building. Do not accept a new outbuilding board without knowing its earthing and protection.
A new circuit commonly needs an Electrical Installation Certificate. It records design, inspection and test results.
Documents to ask for after work
Smaller additions may receive a Minor Electrical Installation Works Certificate. This depends on the work completed.
This guidance is not a fixed electrical design. It does not apply without inspection where an installation is defective or has earthing problems. It also does not apply to a three-phase supply or high-demand commercial use. Specialist machinery, listed properties and conservation restrictions also need an on-site assessment. Speak to Building Control or planning where appropriate.
FAQs
How much does it cost to put electrics in a shed?
A basic fixed supply may cost £800 to £1,800 for a short, accessible run with lights and sockets. Longer routes, trenching, heating allowance or a consumer unit can raise costs to £1,500 to £3,500.
Does a garage need its own consumer unit?
A garage often needs its own consumer unit when it has separate circuits for lights, sockets, a door or heating. The electrician must check load, earthing and protection first.
Can I use an extension lead permanently in my garage?
No. A garage, shed or garden office needs a fixed supply. It needs suitable cable, protection, isolation and testing for the environment and expected load.
Does a loft conversion need new smoke alarms?
A loft conversion may need upgraded alarms where the wider fire-safety design requires them. Check before work starts, as alarms and cabling are harder to add later.
Do I need planning permission for a garage conversion?
Planning permission is not always required, but Building Control approval may still apply. Swansea Council can confirm the position for the property, intended use and external alterations.
What certificate should I get for a new garage circuit?
A new circuit commonly needs an Electrical Installation Certificate with test results. Smaller changes may receive a Minor Electrical Installation Works Certificate, depending on scope.
Can an EV charger share my garage socket circuit?
Usually no. An EV charger needs dedicated design and protective measures. Check supply capacity and Part S duties first.
Get a Swansea quote that can be compared
Request at least two itemised quotes. Each quote should state cable route, expected load and consumer-unit choice. It should also state RCD or RCBO protection, groundworks, testing and certification.
Give each electrician the same equipment list. This lets you compare like with like. It can also avoid costly cable upgrades later.
Learn more
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