Charging an EV from a three-pin plug: cost, time and safety
Charging from a standard UK socket (a “granny cable”) costs exactly the same per kWh as any other home charging — 26.11p/kWh at the July 2026 Ofgem price cap. The trade-off is time: at 2.3 kW, a full charge takes between 16 hr 13 min and 33 hr 55 min across the models we track, versus a typical overnight charge on a 7 kW wallbox.
Prices based on the Ofgem price cap of 26.11 p/kWh, effective 1 July 2026.Source: Ofgem
The cost is the same — the speed is not
Electricity is priced per kWh, not per socket. Whether energy flows through a granny cable or a wallbox, you pay your tariff rate, so a full charge costs the same either way (three-pin charging wastes slightly more energy as heat over its longer sessions — the ~12% loss figure we apply everywhere already covers typical AC losses). What changes is power: 2.3 kW instead of 7kW — roughly a third of the speed.
Full-charge time on a three-pin plug, every model we track
| Model | Usable battery | Empty to full at 2.3 kW | Same charge, 7 kW wallbox | Full-charge cost |
|---|---|---|---|---|
| Fiat 500e | 37.3 kWh | 16 hr 13 min | 5 hr 20 min | £11.07 |
| Nissan Leaf | 39 kWh | 16 hr 57 min | 5 hr 55 min | £11.57 |
| Vauxhall Corsa Electric | 46.3 kWh | 20 hr 8 min | 6 hr 37 min | £13.74 |
| Peugeot e-208 | 46.3 kWh | 20 hr 8 min | 6 hr 37 min | £13.74 |
| MG MG4 EV | 50.8 kWh | 22 hr 5 min | 7 hr 42 min | £15.07 |
| Tesla Model 3 | 57.5 kWh | 25 hr | 8 hr 13 min | £17.06 |
| Volkswagen ID.3 | 58 kWh | 25 hr 13 min | 8 hr 17 min | £17.21 |
| Cupra Born | 58 kWh | 25 hr 13 min | 8 hr 17 min | £17.21 |
| Renault Megane E-Tech | 60 kWh | 26 hr 5 min | 8 hr 34 min | £17.80 |
| BYD Atto 3 | 60.5 kWh | 26 hr 18 min | 8 hr 39 min | £17.95 |
| Smart #1 | 62 kWh | 26 hr 57 min | 8 hr 51 min | £18.40 |
| Volvo EX30 | 64 kWh | 27 hr 50 min | 9 hr 9 min | £18.99 |
| Kia Niro EV | 64.8 kWh | 28 hr 10 min | 9 hr 15 min | £19.23 |
| Hyundai Kona Electric | 65.4 kWh | 28 hr 26 min | 9 hr 21 min | £19.40 |
| Polestar 2 | 67 kWh | 29 hr 8 min | 9 hr 34 min | £19.88 |
| MG ZS EV | 68.3 kWh | 29 hr 42 min | 9 hr 45 min | £20.26 |
| Kia EV6 | 74 kWh | 32 hr 10 min | 10 hr 34 min | £21.96 |
| Hyundai IONIQ 5 | 74 kWh | 32 hr 10 min | 10 hr 34 min | £21.96 |
| Tesla Model Y | 75 kWh | 32 hr 37 min | 10 hr 43 min | £22.25 |
| Volkswagen ID.4 | 77 kWh | 33 hr 29 min | 11 hr | £22.85 |
| Volkswagen ID.7 | 77 kWh | 33 hr 29 min | 11 hr | £22.85 |
| Skoda Enyaq | 77 kWh | 33 hr 29 min | 11 hr | £22.85 |
| Kia EV3 | 78 kWh | 33 hr 55 min | 11 hr 9 min | £23.14 |
Times are energy ÷ power estimates; real sessions can run a little longer. Costs at the July 2026 Ofgem price cap including ~12% charging losses.
Is it safe?
Fine as designed, with rules
Granny cables are built for this job: they limit current (usually to 10 A), monitor temperature at the plug, and stop charging on a fault. Used on a sound, dedicated socket they are a legitimate backup and a normal way to charge a small-battery or plug-in hybrid car.
Never through an extension reel
Hours at 10 A is exactly the load that overheats coiled cables and multi-way adapters. If an extension is unavoidable, it must be fully uncoiled, outdoor-rated and a single heavy-gauge lead — and treated as temporary, not routine.
Check the socket, not just the car
Older wiring, worn sockets and shared circuits are the real risk. If a plug or socket is more than warm to the touch after an hour, stop and have the circuit checked by an electrician before using it for charging again.
When a wallbox wins
Daily-driving a bigger-battery EV from a three-pin plug means the car is rarely full and off-peak windows are too short to fill it. Cheap overnight EV tariffs assume you can take on energy quickly — that is where a 7 kW wallbox pays its way.