How to Check Your EV's Maximum AC Charging Speed

Your EV's maximum AC charging speed is set by the onboard charger inside the car, not by the wallbox or cable you use. A cable or charger can never push electricity into a car faster than the car's onboard charger can accept it, so knowing your car's limit helps you choose the right equipment and avoid paying for capacity you cannot use. The easiest places to find this figure are your owner's manual, the manufacturer's website specifications page, or tools like Zap-Map's vehicle database. If you are matching a cable to your car, our EV charging cable finder makes it straightforward to see the options.

What is the difference between the wallbox output and the car's onboard charger?

These are two separate limits, and the lower of the two always wins. A wallbox might be rated at 7kW or 22kW, but if your car's onboard charger can only accept 7kW, plugging into a 22kW wallbox still delivers only 7kW to the battery. Think of the onboard charger as a funnel: no matter how fast you pour from outside, the funnel's width is the true limit. This is why checking your car's maximum AC rate before buying a wallbox or cable is the right starting point.

Why do some EVs have a 7kW onboard charger while others have 11kW or 22kW?

It comes down to the hardware the manufacturer fitted, which can vary between trim levels of the same model. Single-phase onboard chargers are limited to around 7.4kW on a standard UK home supply. Three-phase onboard chargers can accept 11kW or 22kW, but only on a three-phase supply, which most UK homes do not have. Commercial premises do, which is why 22kW chargers are more common at public sites than at home. Our 22kW three-phase cables are designed for those higher-speed installations.

How does the cable rating relate to the car's charging speed?

A cable's current rating must meet or exceed the current the session will draw. For home charging with a 7kW wallbox, a 32A Type 2 cable is the standard choice. For three-phase public charging at 11kW or 22kW, you need a cable rated accordingly. A cable rated below the session current can overheat, so always match or exceed the charger's output. A higher-rated cable than you need is perfectly safe; you simply will not use its full capacity.

Can my car's maximum AC speed change depending on conditions?

Yes, there are a few reasons why your car may charge more slowly than its rated maximum on a given occasion. Battery temperature is a common factor: most EVs limit charging speed when the battery is very cold or very hot to protect the cells. State of charge also plays a role: many cars slow AC charging as the battery approaches full. The voltage at the supply point can also affect the actual power delivered. So if you see a slightly lower figure than expected during a session, this is often normal behaviour rather than a fault.

Does checking the car's AC speed matter if I only charge at home?

Yes. It tells you whether a 7kW wallbox is the right choice or whether your car would benefit from a higher-rated unit if you have access to a three-phase supply. It also sets realistic expectations for how long an overnight charge takes. If your car has a smaller onboard charger and a larger battery, the manufacturer's website or owner's manual will have the specific figures to work out a rough charge time for your model.

Frequently asked questions

How do I know if my home has a single-phase or three-phase supply?

A qualified electrician can tell you, or you can check your consumer unit: a three-phase supply typically has a larger incomer switch and three separate sets of fuses or breakers. In the UK, the vast majority of domestic properties have single-phase supplies. If you are unsure, ask a registered electrician to confirm before specifying a wallbox.

If my car can accept 11kW, will a 7kW home wallbox slow it down?

Yes, a 7kW wallbox will limit the charge rate to 7kW regardless of your car's 11kW capability. To charge at 11kW you need both a three-phase supply and a charger rated at 11kW. For most home users, 7kW is perfectly adequate for overnight charging. The extra capacity of an 11kW or 22kW onboard charger is more useful at three-phase public chargers.

Can I check my AC charging speed during an active session?

Many EVs display the current charging power on the infotainment screen or in the manufacturer's companion app during an active session. Bear in mind this figure reflects actual draw at that moment, which may be lower than the car's maximum if the battery is nearly full, very cold, or if the supply voltage is slightly below nominal. Use the infotainment display as a useful real-time indicator rather than a strict maximum test.

Does my car's AC charging speed affect how fast it charges at a rapid DC charger?

No. AC and DC charging are separate systems. Your onboard charger handles AC (from a wallbox or public Type 2 post); DC rapid charging bypasses the onboard charger entirely and goes directly to the battery. The AC and DC maximum speeds are listed separately in the manufacturer's specifications. Check both figures if you are planning to use rapid charging on long journeys.

Why does my car charge faster at some public chargers than at home?

Public charge points rated at 22kW and connected to a three-phase supply can deliver more power than a typical 7kW home wallbox, provided your car's onboard charger can accept that higher rate. If your car has a three-phase onboard charger, it can take advantage of higher-output public units in a way that a single-phase home installation cannot match.

Is a 32A cable always the right choice for home charging?

For the majority of UK home wallboxes, which are single-phase units outputting up to 7kW (around 32A at 230V), a 32A Type 2 cable is the standard and correct choice. If you have a three-phase supply and a charger rated at 11kW or 22kW, you will need a cable rated to match. Check the wallbox's output specification and match the cable rating accordingly.

Once you know your car's maximum AC charging speed, matching the right cable becomes straightforward. Browse our Type 2 cables for standard home and public AC charging, or our 22kW three-phase cables if you have access to a higher-output supply. For more guidance on EV charging, visit our Guides section.