EV Charger in a Detached Garage: Long Cable Runs Explained

Yes — you can put an EV charger in or on a detached garage, and installers fit them there routinely. Feasibility is almost never the problem; the cost of getting power to the building is. Running a new armoured-cable supply from your meter position typically costs £800–£2,000 depending on distance (Elec-Mate’s 2026 garage electrical cost guide, last checked July 2026), and three things set the price: how far the cable travels, whether it goes underground or along a wall, and the cable size the run length forces.

How long cable runs are priced

Most installers quote a long run in two parts: the electrical work itself, and the groundwork to get the cable there. For context, Pod Point’s Solo 3S starts from £999 including a standard installation (Pod Point, last checked July 2026) — and long cable runs, trenching and supply upgrades are exactly the things that push a job out of any installer’s “standard” bracket.

Figures from Elec-Mate’s 2026 garage electrical cost guide, last checked July 2026. Your quote will vary with access, ground surface and cable size.

What moves the number: digging through a lawn is cheaper than lifting and reinstating a block-paved driveway; a surface-mounted route along a solid wall can avoid trenching entirely; and digging the trench yourself, to the installer’s written spec, can take a real chunk off. Timber fences are usually ruled out as a cable route — they move, rot and get replaced.

Voltage drop and cable size, in plain English

Electricity loses a little voltage over distance. UK wiring regulations (BS 7671) cap that loss — for a circuit like this the commonly applied limit is 5% of supply voltage, about 11.5V at 230V — so the further the charger sits from the consumer unit, the thicker the cable has to be to stay within it. A 7kW charger draws about 32A; on a short run 6mm² cable is typical, but sizing guidance based on BS 7671 advises stepping up to 10mm² beyond roughly 20 metres. Runs of 30–50m to a detached garage are common, so most garage jobs land in 10mm² territory — one reason they cost more than the per-metre trench rate alone suggests.

Properly sized, a long run does not make charging slower. An undersized one can cause chargers to derate or trip, so if a quote looks suspiciously cheap for the distance, ask to see the voltage-drop calculation.

Buried cable is almost always steel wire armoured (SWA). Common practice is to lay it at around 450mm deep under gardens and 600mm under driveways, on a sand bed with warning tape above — shallower only with extra mechanical protection such as ducting or concrete, and your installer will confirm the depth your ground needs. Ducting is worth having anyway: it turns a future upgrade into a cable-pull rather than a re-dig.

Will the garage need its own consumer unit?

Often, yes — and it’s usually worth it. A small garage sub-board costs about £300–£450 fitted for a 4-way unit (£400–£600 for 6–8 ways), and adding the charger circuit at the same time as the garage supply costs roughly £200–£400, against £600–£1,200 as a later standalone job (Elec-Mate, 2026). If the garage will only ever feed the charger, some installers run the sub-main to a single dedicated circuit instead; either can be compliant, so ask which they’re pricing and why.

Earthing needs a decision too. Where your home has a PME supply, BS 7671 restricts using that earth for EV charging unless the open-PEN fault risk is addressed — typically with a dedicated earth electrode or PEN-fault protection built into the charger, which many modern units now include. And if the charger mounts on the garage’s outside wall, check it carries a weatherproof rating suitable for permanent outdoor exposure, such as IP65 — most reputable home units do.

Permissions, paperwork and the grant

If your property’s maximum demand including the charger is 60A per phase or less, the installer can connect first and notify your electricity network operator (DNO) within 28 days; above that, they must apply to the DNO and wait for its response before installing. A new circuit to an outbuilding is also notifiable under Part P of the Building Regulations in England, and an installer registered with a competent person scheme can self-certify. The installer you choose will check your supply and consumer unit as part of the quote, and should handle both of these for you.

On money: the EV chargepoint grant is worth up to £500 per socket (raised from £350 on 1 April 2026) and, for eligible renters and flat owners, covers 75% of the combined supply-and-install cost up to that cap; homeowners in houses generally no longer qualify, and the OZEV-authorised installer claims it for you. Funding is confirmed until at least 31 March 2027, but because the grant is capped, long-run extras — trenching, 10mm² cable, a sub-board — mostly fall on you. Check the full eligibility rules on GOV.UK before counting on it.

Questions to ask the installer

• Is the price fixed, or is there a per-metre rate if the route turns out longer than measured?
• Who digs the trench — and if I dig it, what depth, bedding and marker-tape spec do you need, in writing?
• What cable size are you using, and can you show me the voltage-drop calculation?
• Will you lay ducting with spare capacity and a draw rope?
• Is a garage consumer unit included, and what’s the spec?
• How are you handling earthing — built-in PEN-fault protection or an earth rod?
• Will you notify the DNO and issue the Building Regulations certificate?

Get two or three quotes against the same route description — find an installer near you or request a free quote — and compare the answers, not just the totals.

Grant rates, wiring regulations and network rules all change. The figures above were last checked in July 2026; for grants, check GOV.UK’s chargepoint grant pages, and for anything specific to your own supply, rely on your installer’s assessment rather than any general guide.