By the HomeEVCharger.co.uk – The UK's Independent EV Charging Guide Team · Updated May 2026 · Independent, reader-supported

Portable EV Charger for Home UK: Granny Cable vs Dedicated Unit Explained

If you've just bought an electric car and can't install a proper wall charger, you might be tempted by the cheapest option: plugging into a standard 13A socket. But there's a world of difference between a "granny cable" and a proper portable EV charger—and it's worth understanding before you commit to either.

What is a Portable EV Charger?

The term "portable EV charger" covers a range of devices, but they fall into two camps: Mode 2 and Mode 3.

Mode 2 chargers work through a standard three-pin UK socket. They're the smallest and cheapest option, often called granny cables or emergency chargers. They suit temporary situations: holidays abroad, emergency top-ups, or short-term cover.

Mode 3 chargers are proper EV-specific units with a Type 2 connector (the standard across Europe). They're designed for regular home charging and are what most installers recommend. Within Mode 3, you get portable units (cable-and-plug variants) or fixed wall boxes—the difference matters for safety and convenience.

This article focuses on Mode 2 granny cables versus genuinely portable Mode 3 units, and when each makes sense for UK homes.

Granny Cable: The Cheap Option with Real Limitations

A granny cable uses your standard 13A domestic socket and typically delivers around 3 kW. Sounds reasonable—until you examine the practical reality.

UK domestic sockets are rated 13A at 230V, but they're not designed for continuous high-current draw. A car charging at the maximum 13A for 8 hours straight will heat the socket, the cable, and anything plugged into it. Over time, this causes degradation. The cable in particular—often thinner than it should be—isn't rated for sustained use at that current.

Most granny cables lack smart load management. Some do include a contactor (a relay that cuts power if fault is detected), but many older or cheaper models don't. Without proper earthing monitoring and circuit protection, there's genuine risk of overheating or electrical damage.

Real-world charging speed is deceptive. A 3 kW charger on a 30 kWh battery takes 10 hours. For a 60 kWh battery (common in modern EVs), you're looking at 20 hours. And that assumes nothing else draws power in your home—the kettle, heating, washing machine all reduce available current.

Dedicated Portable Units: The Sensible Middle Ground

Proper portable EVSEs—units like the Juice Booster 2 or similar Mode 3 chargers—are designed for regular home use without the safety corners cut.

These units include:

• Smart contactor that monitors earth bonding and cuts supply if anything goes wrong
• Thicker cables rated for continuous draw
• Usually 7 kW or 11 kW output (compared to granny cable's 3 kW)
• Type 2 connector, standard across UK and Europe

A 7 kW unit charges a 30 kWh battery in around 4–5 hours. The same 60 kWh battery takes 7–8 hours. That's a material difference over a week of charging.

The trade-off is cost and practicality. A good portable unit costs £400–£700. They're bulkier than granny cables and still need proper installation (circuit breaker, earthing check, often a dedicated 32A circuit). If you're moving house frequently, you might not want to carry one around.

Charging Speeds: Real Numbers

This is where the choice becomes clearest:

• Granny cable (3 kW): 30 kWh battery = 10 hours. 60 kWh battery = 20 hours.
• Portable 7 kW unit: 30 kWh battery = 4–5 hours. 60 kWh battery = 7–8 hours.
• Wall-mounted 7 kW: Same as portable unit (7 kW), but fixed in place.
• Wall-mounted 11 kW: 30 kWh battery = 3 hours. 60 kWh battery = 5–6 hours.

If you're charging overnight twice a week, a granny cable works. If you're charging daily or need flexibility, speed matters more than you might think.

Safety: Why a Proper Charger Matters

This is non-negotiable. A granny cable using a standard socket bypasses several safety mechanisms:

• No earth-bond monitoring: Modern EV chargers continuously check that the car's earth connection is sound. A fault here can be dangerous. Granny cables don't do this.
• Thermal risk: 13A continuous into a standard plug and socket generates heat. The connection loosens over time, which generates more heat.
• Overload vulnerability: If something else is plugged in nearby, total circuit load can exceed what the wiring safely handles.

A proper portable EV charger includes thermal monitoring, earth detection, and a smart contactor that cuts supply if anything goes wrong. It's also installed by someone who checks your home's earthing and circuit protection.

If you use a granny cable, have an electrician verify your earthing is sound and install a dedicated 13A circuit breaker for the socket. Do not plug it into a standard extension lead or shared socket.

Cost Reality

• Granny cable: £30–£100. Installation: DIY (or call an electrician to check earthing, roughly £100–£200).
• Portable 7 kW unit: £400–£700. Installation: £300–£600 (circuit work, earthing check).
• Wall-mounted 7 kW unit: £400–£600 for the charger. Installation: £800–£1,500 (requires circuit work and wall mounting).

Wall units are fastest and most convenient long-term, but require permanent installation. For renters or those moving house, a portable unit offers better value than a wall box plus the cost of removal and reinstallation.

When Portable Is the Right Choice

A proper portable EV charger makes sense if you:

• Rent your home or may move within 3–5 years
• Don't have permission to install a wall unit
• Need the flexibility to charge at different locations (though this is rarer than marketing suggests)
• Want to upgrade from a granny cable but aren't ready for permanent installation

A granny cable is honest choice only if:

• You charge no more than once weekly
• You have a short-term need (holiday backup, emergency)
• You understand the thermal and safety limits and have an electrician verify your installation

The Wall Unit Reality Check

For most UK home EV owners, a proper wall-mounted charger is the long-term winner. At £1,200–£2,000 all-in, it's a one-time cost. You get 7–11 kW charging, it lasts 10+ years, and your car charges safely every night. If you own your home, this is typically cheaper per charge than anything else.

But that's not always an option—and if it's not, a proper portable unit outpaces a granny cable by enough that the extra cost pays for itself in convenience and peace of mind within 12–18 months of regular use.