Granny Charger Buying Guide: What to Look For

A good granny charger comes down to five things: the current it draws, the plug type, the cable length, whether you can adjust the amperage, and the build quality of the control box and connectors. Most portable EV chargers plug into a standard 3-pin UK socket and add roughly 8 to 10 miles of range per hour, so they suit occasional and backup charging rather than daily high-mileage use. Before you buy, match the car end to your inlet and browse our portable EV chargers to compare options. This guide walks through what actually matters so you do not overpay for features you will never use.

At a glance: what to look for

How many amps should a granny charger draw?

Aim for a charger that draws around 10A, roughly 2.3kW, from a standard 3-pin socket. That is the sensible ceiling for a normal domestic socket over a long charge. Some chargers let you step down to about 8A or 6A, which is genuinely useful on older wiring, a shared circuit, or when you just want to be cautious overnight. Do not chase higher-current portable units that need a special commando or blue socket unless you already have that socket fitted, because a normal 3-pin outlet cannot safely deliver more than around 10A continuously.

Why does adjustable current matter?

Adjustable current is one of the most useful features on a granny charger. It lets you reduce the draw to suit the socket you are plugging into. On an older house, a garage on a shared circuit, or a socket you are not certain about, dialling down to 8A or 6A lowers the heat load and the risk of tripping. You charge a little slower, but far more safely. If you often charge away from home in unfamiliar sockets, an adjustable unit is worth prioritising over a fixed 10A model.

Does the plug and car connector need to match my car?

Yes, and this is the part people get wrong. The wall end should be a standard UK 3-pin plug. The car end must match your inlet: Type 2 for virtually every EV and plug-in hybrid sold since 2018, or Type 1 for some older cars such as early Nissan Leaf and early Mitsubishi Outlander PHEV. If you are unsure which you have, our Type 1 vs Type 2 guide explains how to tell them apart. The wrong car connector simply will not plug in.

What cable length should you choose?

Pick the shortest length that comfortably reaches. A 5m cable suits most driveways and garages where you park close to the socket. Go for 7m or 10m if the socket is awkwardly placed, the charging inlet is on the far side of the car, or you sometimes park further away. Remember that longer cables are heavier to handle and coil, so do not buy 10m if 5m always reaches. A tidy, well-fitting length is easier to live with day to day.

What build-quality details separate a good unit from a cheap one?

Look at the control box and connectors first. A quality granny charger has a solid, well-sealed control box with built-in temperature and fault protection that cuts power if the plug gets too hot. Good connectors feel firm and click home rather than feeling loose. A status display or clear indicator lights help you confirm it is charging. Weatherproofing claims vary, so only rely on an ingress rating if the specific product listing states it. A reassuring warranty and a recognised safety standard on the box are both good signs.

Frequently asked questions

How fast does a granny charger add range?

A typical granny charger draws around 2.3kW and adds roughly 8 to 10 miles of range per hour. Over a full overnight charge that can be enough for many everyday drivers, but it is slow compared with a 7.4kW wallbox that adds around 25 to 30 miles per hour. Treat it as a top-up and backup tool rather than a fast daily solution.

Can I leave a granny charger plugged in overnight?

Yes, provided it is plugged directly into a suitable wall socket on a sound circuit, with no extension lead or adapter. Overnight is exactly when many people use one. Choose a unit with temperature protection, check the plug is not running hot during the first few charges, and if you have any doubt about the socket, have an electrician confirm the wiring.

Do I need a 22kW portable charger?

No. Portable granny chargers work from a standard 3-pin socket at around 2.3kW, and no domestic 3-pin socket can deliver 22kW. High-power charging needs a dedicated wallbox or public point. If you want faster home charging, a wallbox is the answer, not a higher-rated portable unit plugged into a normal socket.

Is a granny charger enough as my only charger?

For low-mileage drivers who can leave the car plugged in overnight, it can be. For higher-mileage drivers it is usually too slow to fully recover range each night. Many owners use a granny charger as a backup and travel kit, and fit a wallbox for daily charging. Match the choice to how far you actually drive.

Will a granny charger work with my plug-in hybrid?

Usually yes. Plug-in hybrids have smaller batteries, so a granny charger can often refill them overnight comfortably. Just check whether your PHEV uses a Type 2 or an older Type 1 inlet and buy the matching car connector. The smaller battery is why granny charging suits many hybrids well.

Are cheap granny chargers safe?

Some are fine and some are not, so buy on build quality rather than price alone. Look for temperature and fault protection, solid connectors, a clear safety standard on the box, and a warranty. A charger that runs continuously for hours needs to be well made, so it is not the place to cut corners with an unbranded bargain of unknown origin.

In short, buy for the socket you have and the car you drive: around 10A, the right car connector, a sensible length, adjustable current if you can, and a solid control box. For deeper reading, see our roundup of the best portable EV chargers in the UK and our granny charger vs wallbox comparison. When you are ready to buy, browse our full range of portable EV chargers.