How Does EV Charging Work? A Beginner's Guide

EV charging works by feeding electricity into your car's battery, either as alternating current (AC) that the car converts using its onboard charger, or as direct current (DC) that flows straight to the battery at rapid speeds. At home and on most public AC points you plug in a Type 2 charging cable, and the car handles the conversion, which is why AC charging is slower but simpler. Rapid DC chargers do the conversion themselves and are always tethered, so you never bring your own cable for those. The connector on the charger end is Type 2 for AC in the UK, while the car end must match your car's inlet.

At a glance: how EV charging works

What is the difference between AC and DC charging?

The key difference is where the conversion happens. Batteries store DC, but the grid supplies AC, so the current must be converted at some point. With AC charging, your car's onboard charger does the conversion, which limits speed to what that charger can handle, often 7.4kW or 11kW. With DC rapid charging, the charger itself converts to DC and sends it straight to the battery, bypassing the onboard charger, which is why rapid charging is measured in minutes rather than hours.

What is the onboard charger?

The onboard charger is the unit inside your car that converts AC from a home or public AC point into the DC your battery stores. Its rating sets your maximum AC charging speed. If your onboard charger is rated at 7.4kW, that is the fastest you will charge on AC, even on a 22kW charger. This is why a bigger AC cable does not always mean faster charging: the weakest link, whether the supply, the cable or the onboard charger, decides the speed.

What connectors are used in the UK?

The UK standard is Type 2 (Mennekes) for AC charging, fitted to every EV and plug-in hybrid sold since 2018. For rapid DC charging, most cars use CCS, which is a Type 2 connector with two extra DC pins below it, while some older cars use CHAdeMO. A few older vehicles have a Type 1 AC inlet instead of Type 2. Your cable's car end must match your car's inlet, while the charger end for AC is always Type 2.

Quick connector guide

• Type 2: UK AC standard, locks while charging, up to 22kW AC
• Type 1: older single-phase AC, up to about 7.4kW, no locking latch
• CCS: rapid DC, Type 2 plus two DC pins
• CHAdeMO: older rapid DC standard on some cars

How fast will my car charge?

Your charging speed depends on the slowest link in the chain: the power supply, the cable, and your car's onboard charger. On a standard UK home, 7.4kW is the ceiling and adds roughly 25 to 30 miles of range per hour. A 3-pin portable charger delivers around 2.3kW, adding roughly 8 to 10 miles per hour, so it suits occasional use. Rapid DC chargers of 50kW to 350kW are far faster, but they are separate from home AC charging and are always tethered.

What do I need to start charging at home?

To charge at home you need a suitable connection point and the right cable. Most home wallboxes are untethered, so you use your own Type 2 to Type 2 cable, usually 5m for a typical driveway. A 3-pin portable charger is a slower alternative, but it must plug directly into a wall socket on its own circuit, never through an extension lead, multi-way adapter or smart plug, as that creates a fire risk. Match the cable's car end to your car's inlet and you are ready to charge.

Frequently asked questions

How does EV charging actually work?

Charging feeds electricity into your battery, either as AC that your car's onboard charger converts to DC, or as DC delivered straight to the battery by a rapid charger. AC charging at home and on public AC points is slower but simpler and uses your own Type 2 cable. Rapid DC charging is much faster and always uses the charger's own tethered cable.

What is an onboard charger?

The onboard charger is the unit inside your car that converts AC electricity into the DC your battery stores. Its rating, often 7.4kW or 11kW, sets your maximum AC charging speed. Even on a more powerful AC charger, you cannot exceed your onboard charger's rating, which is why a bigger cable alone does not make AC charging faster.

Do I need my own cable to charge?

For untethered AC points, including most home wallboxes and many public AC chargers, yes, you plug in your own Type 2 cable. For rapid DC chargers the cable is attached, so you never bring your own. Keeping a Type 2 lead in the boot means you can use both home charging and untethered public AC points.

What connector does my car use?

Every EV sold in the UK since 2018 uses Type 2 for AC charging. Some older cars use the earlier Type 1 AC inlet. For rapid DC, most cars use CCS, which adds two DC pins below the Type 2 connector, while some older vehicles use CHAdeMO. Your cable's car end must match your car's inlet.

Why is rapid charging so much faster?

Rapid charging is faster because the charger converts electricity to DC itself and sends it straight to the battery, bypassing your car's onboard charger. That removes the AC speed limit set by the onboard charger. Rapid chargers run from 50kW up to 350kW, so a useful top-up takes minutes rather than the hours needed on home AC.

Can I charge from a normal plug socket?

Yes, using a 3-pin portable charger, but it is slow at around 2.3kW, adding roughly 8 to 10 miles of range per hour. It must plug directly into a wall socket on its own circuit, never through an extension lead, multi-way adapter or smart plug. It is a useful backup rather than a fast everyday solution.

Once you understand AC versus DC and the role of the onboard charger, choosing the right kit is straightforward. Read our deeper dive on AC vs DC EV charging and our guide to Type 1 vs Type 2 connectors, then match a lead to your car on the cable finder.