A granny charger is the informal name for the Mode 2 cable that comes with every electric vehicle a cable that connects your car to a standard 13A domestic plug socket and charges the battery at approximately 2.3kW. It is called a granny charger because it is slow, not because it is outdated or unsafe when used correctly. Every new EV includes one, it requires no installation, and it works anywhere there is a standard UK socket. The honest answer to whether you should use one is: for emergency top-ups and occasional use away from home, yes. As your primary daily charging solution at home, no it is too slow for most modern EVs and places a continuous high load on a domestic socket that is not designed for ten-hour overnight charging sessions. This guide covers exactly what a granny charger is, when it is appropriate, when it is not, and why a dedicated 7kW wallbox is the right long-term solution for home charging.
What a Granny Charger Actually Is
The term granny charger refers to a Mode 2 charging cable the classification refers to the type of connection it makes between the car and the power source.
Mode 1 a direct connection between the vehicle and a standard socket with no in-cable safety device. Not legal for EV use in the UK.
Mode 2 a connection between the vehicle and a standard socket via an in-cable control box (ICCB In-Cable Control Box). The ICCB is the box partway along the cable that contains the safety electronics: it monitors the connection, checks earth continuity before allowing current to flow, provides RCD protection, and can detect faults that would make it unsafe to continue charging. This is what every manufacturer-supplied granny charger is.
Mode 3 a connection between the vehicle and a dedicated EV charge point with its own built-in safety and communication electronics. This is what a 7kW wallbox installation provides.
Mode 4 a DC rapid charging connection. This is what motorway rapid chargers use.
The ICCB in a Mode 2 cable is genuinely important it is not a simple extension lead. The safety device inside it is what makes granny charging reasonably safe rather than simply plugging into a domestic socket. The risk with granny charging is not the cable itself. It is the condition of the socket it is plugged into, the circuit it draws from, and the duration and frequency of use.
How Fast Does a Granny Charger Charge?
A granny charger connected to a standard 13A UK socket delivers approximately 2.3kW. This translates to roughly 8–10 miles of range per hour of charging.
| Battery size | Granny charger time (empty to full) | 7kW wallbox time |
| 17kWh (e.g. PHEV) | ~7.5 hours | ~2.5 hours |
| 40kWh (e.g. Nissan Leaf base) | ~17 hours | ~5.7 hours |
| 60kWh (e.g. VW ID.4 standard) | ~26 hours | ~8.5 hours |
| 77kWh (e.g. Hyundai IONIQ 5) | ~33 hours | ~11 hours |
| 100kWh (e.g. Tesla Model S Long Range) | ~43 hours | ~14 hours |
For plug-in hybrids with smaller batteries, a granny charger is genuinely adequate a 17kWh PHEV battery charges fully in a comfortable overnight window. For full EVs with modern larger batteries, the picture is very different. A 60kWh battery takes over 26 hours to charge from empty on a granny charger more than a full day. Even adding 50 miles of range takes approximately five hours.
This is not just an inconvenience. A driver who relies on a granny charger for daily charging will regularly find themselves unable to recover the range they used during the day in a single overnight session.
The Safety Question: Is a Granny Charger Safe?
Used correctly on a good quality, well-maintained socket, for occasional rather than daily overnight sessions a granny charger is reasonably safe. The ICCB provides genuine protection against faults.
The specific safety considerations that make regular overnight granny charging inadvisable:
Continuous load on a domestic socket
A standard 13A socket and the circuit it sits on are designed for intermittent use. Kettles, toasters, and phone chargers draw current in short bursts. A granny charger draws continuous current at 10A for eight, ten, or more hours at a stretch.
Most domestic sockets are rated for 13A intermittent use, not sustained overnight loads. The connections within the socket the plug contacts, the socket contacts, the wiring terminals behind the socket experience heat from sustained current draw that they would not experience from intermittent appliance use. Over repeated sessions, this heat cycling can loosen connections, degrade insulation, and create fault conditions.
An EV charger circuit properly installed to BS 7671 Section 722 uses appropriately rated cables, an RCBO on a dedicated circuit, and contacts designed for sustained load. A domestic socket behind a shared ring main is not the equivalent, however the ICCB makes it appear so.
Socket and circuit condition
The safety of any granny charging session depends entirely on the condition of the socket it is plugged into. A socket with loose contacts, aged wiring, inadequate earthing, or a circuit that is already near capacity with other loads introduces risks that the ICCB cannot fully protect against.
This is particularly relevant for:
- Older properties with aging electrical installations
- Garage sockets that may not have been regularly inspected
- Extension leads granny chargers should never be used with an extension lead. The ICCB is designed to operate with a direct socket connection, not through additional cable
The extension lead prohibition
Never use a granny charger with an extension lead or a multi-socket adapter. The ICCB’s earth continuity check and fault protection are calibrated for a direct socket connection. Extension lead contacts introduce additional resistance, potential poor earth continuity, and overheating risk that the ICCB cannot account for. Every EV manufacturer and the Electrical Safety First guidance agrees on this point.
When Granny Charging Is Perfectly Fine
With those caveats stated clearly, there are situations where granny charging is entirely appropriate:
Occasional use when away from home. Staying at a friend’s house, a holiday cottage, or any location without a dedicated charge point connecting to a convenient socket to add some range overnight is a reasonable use of the granny charger. One session, a well-maintained socket, no extension lead.
PHEVs and small battery EVs used for short commutes. A plug-in hybrid with a 15–20kWh battery and a daily commute of 20–30 miles electric range can be fully recharged overnight on a granny charger without any timing issues. The combination of small battery and low daily mileage means the slow charge rate is not a practical problem.
Emergency top-up during a journey. If you need a small amount of range to reach a faster charging point or your destination, a granny charger at a convenient socket provides a slow but meaningful boost. A few hours on a granny charger might add 25–30 miles enough to get somewhere more convenient.
Temporary use immediately after taking delivery. Before a dedicated wallbox has been installed, a granny charger allows immediate use of the vehicle. This is its most common UK use case most owners who take EV delivery on a Friday can get through the weekend on a granny charger before a wallbox installation the following week.
When Granny Charging Is Not Appropriate
As the primary home charging solution for a full EV. Daily granny charging of a vehicle with a 60kWh+ battery puts a sustained overnight load on a domestic socket every night, takes far longer than an overnight window allows for a depleted battery, and is not the solution the vehicle or the socket was designed for.
On sockets of unknown or questionable condition. An older garage socket, a socket that has never been tested, or any outlet where the circuit condition is uncertain is not appropriate for regular overnight EV charging.
With any extension lead. No exceptions. Direct socket connection only.
When other high-draw appliances share the same circuit. Granny charging on a shared ring main circuit that also carries a tumble dryer, an electric shower, or other high-draw appliances creates overload risk on the shared circuit. The granny charger draws the maximum the socket offers there is no headroom for simultaneous demand from other appliances on the same circuit.
Granny Charger vs Dedicated Wallbox: The Key Differences
| Feature | Granny charger (Mode 2) | Dedicated 7kW wallbox (Mode 3) |
| Charging speed | ~2.3kW (8–10 miles/hour) | ~7kW (25–30 miles/hour) |
| Circuit type | Shared domestic ring main | Dedicated 32A protected circuit |
| Installation required | None | Yes qualified electrician |
| Safety protection | In-cable ICCB | RCBO on dedicated circuit + smart protection |
| Smart scheduling | Not available | Standard on all new UK installations |
| Suitable for daily charging | Not recommended for full EVs | Yes |
| Grant eligible | No | Yes for eligible properties |
| Cost | Included with vehicle | £750–£1,350 installed |
The wallbox costs more upfront but the combination of faster charging, dedicated circuit safety, smart off-peak scheduling, and grant eligibility makes it the correct long-term solution for any homeowner planning to charge a full EV regularly at home.
The Cost Argument for a Wallbox Over Granny Charging
Granny charging is free in the sense that no installation is required. But the indirect costs add up quickly.
Electricity cost: Without smart off-peak scheduling which granny chargers cannot do you charge whenever you plug in, including during peak hours at 25–35p/kWh. A 7kW smart wallbox scheduled to charge overnight on an off-peak tariff at 7p/kWh saves approximately £600–£900 per year on electricity costs compared to peak-rate charging. Over three years of ownership, that saving typically exceeds the cost of the wallbox installation.
Time cost: Waiting 26+ hours to fully charge a 60kWh battery on a granny charger rather than 8–9 hours on a wallbox is a practical daily inconvenience that compounds across years of ownership.
Grant eligibility: For eligible homeowners, the OZEV grant reduces the cost of a wallbox installation by up to £500 further closing the gap between the apparent cost of granny charging (zero) and the actual net cost of a properly installed wallbox. See our EV charger grants guide for eligibility criteria.
What to Do If You Are Currently Relying on Granny Charging
If you took delivery of an EV recently and are using the granny charger as a temporary measure, the right next step is arranging a wallbox installation. The process is straightforward: a site survey, a written quote, and an installation that typically takes two to four hours on the day. See our guide to how long EV charger installation takes for what the process involves.
If granny charging is working for you because you drive a PHEV or a small battery EV with a short daily commute, it is a reasonable ongoing solution subject to using a good quality, dedicated socket and never using an extension lead.
If you are considering whether your current socket is in a suitable condition for continued EV charging, an electrician can inspect and confirm the socket and circuit condition as part of a site survey visit.
“`htmlFrequently Asked Questions
What is a granny charger for an EV?
A granny charger is the Mode 2 charging cable that commonly comes with an electric vehicle. It connects the car to a standard 13A domestic plug socket and typically charges at approximately 2.3kW, adding around 8–10 miles of range per hour. It is called a granny charger because of its relatively slow charging speed. The cable includes an in-cable control box (ICCB) with built-in safety electronics that monitor the connection and provide RCD protection before current flows.
Is it safe to charge an EV with a granny charger?
For occasional use on a well-maintained, good-quality socket, a granny charger can be used safely when the vehicle manufacturer’s instructions are followed. The ICCB provides important safety protection. However, regular overnight daily charging is generally not recommended because a domestic socket and circuit may not be designed for this sustained load. A dedicated 7kW wallbox provides a safer and faster long-term charging solution for most EV owners.
Can I use a granny charger every night?
Using a granny charger every night is generally not recommended for a full EV. Nightly charging draws continuous current through a domestic socket and circuit that may not have been designed for this type of sustained load. For plug-in hybrid vehicles (PHEVs) with smaller batteries or drivers with low daily mileage, the practical impact may be lower, but a dedicated wallbox remains the safer and faster long-term charging solution.
Can I use a granny charger with an extension lead?
No. A granny charger should be plugged directly into a suitable domestic wall socket rather than an extension lead. Extension leads can introduce additional resistance, poor connections and overheating risks, particularly when carrying a continuous charging load. Always follow the EV manufacturer’s instructions and use the charger as specified.
How much faster is a 7kW wallbox than a granny charger?
A 7kW wallbox can charge an EV at roughly three times the power of a typical 2.3kW granny charger. A granny charger may add around 8–10 miles of range per hour, while a 7kW wallbox can typically add around 25–30 miles of range per hour, depending on the vehicle. As an example, a 60kWh battery could take around 8–9 hours to charge from near-empty using a 7kW wallbox, compared with roughly 26 hours using a 2.3kW granny charger.
Is it worth installing a wallbox if I already have a granny charger?
Yes, for most full EV owners. A dedicated wallbox can charge around three times faster than a granny charger and operates through an electrical installation designed for EV charging. Smart wallboxes can also support scheduled off-peak charging, which may reduce electricity costs when used with a suitable time-of-use tariff. Depending on your circumstances, you may also qualify for EV charger grant funding. The overall value depends on your electricity tariff, driving habits, vehicle and installation cost.
Can I charge my EV from a caravan hook-up point or industrial socket?
Some EV charging cables are supplied with or support adaptors for blue CEE-form sockets, which can be found at campsites and some worksites. These connections may provide a more suitable sustained electrical supply than a standard domestic socket in certain situations. However, compatibility depends on the vehicle, charging cable, socket and electrical installation. Always check your vehicle’s handbook and the charger’s specifications before using a caravan hook-up point or industrial socket.
Upgrade From Granny Charging to a Dedicated Wallbox
If you’re ready to move from temporary granny charging to a properly installed home wallbox, EV Install Pro provides OZEV-approved, NICEIC-registered home EV charger installation across London, including Barking & Dagenham, Barnet, Bexley, Brent, Bromley, Camden, Croydon, Ealing, Enfield, Greenwich, Hackney, Hammersmith & Fulham, Haringey, Harrow, Havering, Hillingdon, Hounslow, Islington, Kensington & Chelsea, Kingston upon Thames, Lambeth, Lewisham, Merton, Newham, Redbridge, Richmond upon Thames, Southwark, Sutton, Tower Hamlets, Waltham Forest, Wandsworth, and Westminster.
Every installation includes a site survey before quoting, smart charger configuration, DNO notification, and a full Electrical Installation Certificate. For the full picture of what a home installation costs, see our EV charger installation cost guide. For grants that may apply to your installation, see our EV charger grants guide. For a comparison of charger power outputs, see our 3kW vs 7kW vs 22kW guide.
Contact us to arrange a no-obligation site survey and written quote.
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