Installing an EV charger is usually straightforward when the parking space is beside the house. However, many homes across Redhill and Surrey have detached garages, long frontages, garage courts, shared driveways or outbuildings some distance from the main property.
That distance does not prevent a safe and reliable installation, but it does change the design. The cable route, voltage drop, earthing arrangement, protective devices and groundworks all need to be considered before the work begins.
For EV charger installation Surrey homeowners can rely on, the right approach is to survey the complete route rather than simply choosing a charger and extending the nearest cable.
Why distance matters to an EV charger
A typical home charger delivers around 7kW at approximately 32 amps on a single-phase supply. It is a substantial continuous electrical load, particularly when it is installed at the end of a long cable run.
The longer the cable, the greater the voltage drop. Excessive voltage drop can affect charging performance and may mean the circuit does not meet the design requirements of BS 7671.
A short run may use 6mm² cable in suitable conditions, but it is not good practice to assume that a standard 6mm² run will be adequate to a detached garage. For a longer external route, the cable will often need to be steel wire armoured (SWA), either buried or securely clipped to a suitable surface.
As a broad guide:
- Up to approximately 25–30 metres may be relatively straightforward with 6mm² SWA, subject to full calculations.
- Between approximately 30 and 80 metres will often require 10mm² SWA or larger.
- Very long runs may require 16mm² cable, a revised charging arrangement or a more detailed electrical design.
These are not fixed distance limits. Cable size depends on the actual length, installation method, grouping, ambient conditions, upstream wiring, charger rating and protective device. The electrician should calculate voltage drop and current-carrying capacity rather than selecting cable based on distance alone.
For example, a 40-metre run to a garage may be better served by 10mm² SWA than 6mm², even though both cables could appear suitable at first glance. Increasing the cable size at the installation stage is usually far less disruptive than replacing an undersized cable after a driveway has been reinstated.
When a separate garage consumer unit makes sense
For a short run serving only one charger, a dedicated circuit from the main consumer unit may be appropriate.
A detached garage or outbuilding becomes more involved when:
- The route is particularly long.
- The garage already has lighting or socket circuits.
- You want power for tools, a freezer or workshop equipment.
- You plan to install garden lighting from the same area.
- You may want a second EV charger in the future.
- The existing supply is old, damaged or difficult to test.
- Several buildings or external loads need to be supplied.
In these situations, a properly designed SWA sub-main feeding a small consumer unit in the garage can be the better solution. The garage board can then supply the EV charger, lighting and sockets through separate circuits, with suitable isolation and protection.
This does not automatically make the installation cheaper or allow a smaller cable. The sub-main still needs to be sized for the expected load and voltage drop. Its advantage is that it creates a safer, more flexible distribution point and avoids running several separate cables from the house.
Earthing a detached garage or outbuilding
Earthing is one of the most important differences between a charger beside the house and one at the end of a driveway.
The property may have a TN-S, TN-C-S (PME) or TT earthing arrangement. Many modern homes have a TN-C-S supply, often referred to as PME. In a detached building, simply extending the house earth without checking the arrangement can create additional risks, particularly where the vehicle or charger could be in contact with true Earth.
BS 7671 Section 722 includes specific requirements for EV charging. Where a charge point is outdoors, or could reasonably be used to charge a vehicle parked outdoors, the installation must address the risk associated with an open-PEN fault.
Depending on the property and charger, the solution may include:
- A charger with suitable built-in PEN fault detection.
- An external open-PEN protection device.
- A separate TT earthing arrangement with an earth electrode.
- Another compliant protective arrangement selected during the design.
A modern charger may include PEN fault detection, but this should never be assumed from appearance alone. The installer must check the manufacturer’s instructions and confirm that the equipment is suitable for the proposed earthing arrangement.
If a TT arrangement is required, the earth electrode, protective devices and RCD arrangements must be designed and tested correctly. The detached garage may need to be treated as a separate earthing environment, particularly if it contains other electrical equipment or extraneous conductive parts.
The EV circuit must also use separate neutral and protective conductors. A PEN conductor should not be carried through the EV final circuit.
The IET’s guidance on EV charging equipment installation explains why these arrangements need to be considered as part of the overall design, rather than added as an afterthought.
Trenching, ducting and working across a driveway
There are two main ways to reach a detached garage:
- An underground route, usually involving a trench across the garden, driveway or access path.
- A clipped or supported surface route, where the cable is installed along a wall, fence line or other suitable structure.
An underground installation usually provides the neatest finish, but it may involve lifting block paving, tarmac, concrete or landscaping. The route should be planned to avoid drainage, water pipes, telecoms and other buried services. Armoured cable should be installed with appropriate mechanical protection, ducting where required, suitable bedding and warning tape.
A duct can also make future replacement or upgrading easier, although it must be sized and installed correctly. It is not a substitute for selecting the correct cable and protection.
A surface route may avoid digging, but the SWA must be properly supported, protected from impact and terminated using suitable glands and accessories. Cable entries into the house or garage also need appropriate sealing, mechanical protection and fire-stopping where necessary.
If the driveway is being resurfaced, or a landscaper is already installing paving, drainage or garden walls, it is often sensible to coordinate the electrical work at the same time. ADS Electrical can liaise with landscapers, groundworkers and other trades so the cable route is installed before surfaces are closed.
Plan other garage power at the same time
A long cable route is often the most disruptive part of the job. If the trench is being opened or a sub-main is being installed, it may be cost-effective to plan other requirements at the same time.
These might include:
- Internal garage lighting.
- External or garden lighting.
- General-purpose sockets.
- Power for a freezer, workshop or door equipment.
- A future second EV charger.
- Security equipment such as CCTV.
- Lighting for a driveway, pathway or garage court.
ADS Electrical offers free lighting design consultations where appropriate, which can be useful when planning garage, garden or driveway lighting alongside the EV installation. Designing the complete requirement together can reduce duplicated labour and avoid reopening a finished driveway later.
Two chargers, load management or moving the charger?
A second EV charger may make sense where two vehicles are regularly parked at the property. However, two 7kW chargers could demand more power than the home’s supply or existing installation can comfortably provide.
Options may include:
- Load management, allowing chargers to share available capacity.
- A larger or redesigned sub-main.
- Charging one vehicle at a time.
- Installing one charger in the garage and another closer to the house.
- Relocating the charger to a more practical parking position.
Sometimes the best answer is not to run power to the furthest garage. If the vehicle is usually parked closer to the house, a shorter charger circuit may reduce groundworks, cable size and cost. A site survey should consider how the vehicle is actually used, not just where the garage is located.
Local considerations around Redhill and Surrey
Older properties in Redhill, Reigate, Merstham, Nutfield, Salfords and surrounding villages can have long frontages, detached garages and electrical installations that have been extended over several decades.
Shared driveways and garage blocks also create additional questions about access, responsibility for repairs and permission to install cables across common areas. In these situations, written consent and early coordination can prevent delays.
Many Surrey homes still have single-phase supplies, so the charger rating, existing household demand and any planned second charger should be reviewed together.
ADS Electrical is a NICEIC Approved Contractor providing domestic, commercial and industrial electrical services. We offer free quotes within 24 hours, clear communication throughout the project and a fast, efficient service. For advice on a detached garage or long driveway, contact us on 07870 554498 or request a home charging point Surrey quotation.
Pre-install checklist
Before arranging the installation, it helps to confirm:
- The approximate one-way distance from the consumer unit to the charger.
- Whether the route crosses a driveway, shared access or third-party land.
- Whether the charger will be used only inside the garage or may charge a vehicle outdoors.
- The property’s existing earthing arrangement, if known.
- Whether the garage already has power, lighting or sockets.
- Whether you may want a second charger or additional garage loads.
- The position of drainage, water, telecoms and other buried services.
- Whether landscaping or resurfacing work is already planned.
- Where the vehicle will normally be parked while charging.
Frequently asked questions
Is there a maximum distance for an EV charger?
There is no single maximum distance. The practical limit depends on voltage drop, cable size, protective devices, earthing, installation method and the available capacity of the property. Runs over approximately 25–30 metres usually need more detailed cable calculations.
Do I need permission to dig up my own driveway?
Planning permission is not normally required simply to install a private electrical cable on your own property. However, you should check the position if the driveway is shared, the route reaches a public highway, the property is listed or in a conservation area, or another party owns part of the access. Buried services must also be identified before excavation.
Can my existing garage supply be reused?
Possibly, but it must be inspected and tested. The existing cable may be too small, lack suitable earthing or protection, have suffered damage, or be unsuitable for the continuous load of an EV charger. An old garage supply should not be reused without verification.
How long does installation take?
A straightforward charger installation may be completed in a day. A long-distance installation involving trenching, driveway reinstatement, a new garage consumer unit or coordination with other trades may take longer: often one to several working days depending on access and ground conditions.
Is a charger with PEN fault detection always enough?
Not necessarily. The charger must be suitable for the installation and used in accordance with its manufacturer’s instructions and BS 7671 Section 722. In some properties, a TT earth electrode or another protective arrangement may be required.
If you are looking for reliable electric car charger installers Surrey homeowners and businesses can trust, ADS Electrical can assess the route, explain the options and provide a clear quotation before work begins. We also provide 24-hour emergency call-outs for urgent electrical faults on 07870 554498.