How to Read a Public Charger's Power Rating

A public charger's power rating, shown in kilowatts (kW), tells you how quickly it can deliver energy to your battery, but the actual speed you experience depends on what your car can accept. Higher kW means faster charging, up to the limit your vehicle's onboard systems allow. A 50 kW rapid charger connected to a car with a 50 kW DC charge limit will charge at 50 kW; the same charger connected to a car limited to 25 kW will only deliver 25 kW. Understanding this before you arrive saves confusion and helps you pick the right charger for your stop. Check the charging cables guide to confirm which connector type your car uses before heading out.

What does kW actually mean on a charger screen?

Kilowatts (kW) measure the rate of power delivery, not the total amount of energy. Think of it like water pressure rather than total volume. A charger rated at 22 kW delivers energy twice as fast as one rated at 11 kW, all else being equal. The number displayed on a charger's screen or listed on the network's app is the charger's maximum output. Your car will draw up to that maximum, but never more than its own charge rate allows. Always check both the charger's rating and your car's maximum charge rate before assuming you will get the fastest possible speed.

What is the difference between AC and DC charging?

AC (alternating current) charging passes electricity through your car's onboard charger, which converts it to DC (direct current) for the battery. This conversion process limits the speed: most onboard chargers handle up to 7 kW, some up to 11 kW or 22 kW on three-phase power. DC (direct current) charging bypasses the onboard charger entirely and feeds the battery directly, which is why DC rapid chargers can deliver 50 kW, 100 kW, or more. The trade-off is cost and physical size: DC chargers are more expensive to install, which is why rapid and ultra-rapid chargers appear at motorway services and dedicated hubs rather than car parks and supermarkets.

How do I know how fast my car will actually charge?

Your car has two limits you need to know:

• Maximum AC charge rate: set by the onboard charger. Common values are 7 kW, 11 kW, and 22 kW. Connecting to a 22 kW AC charger when your car tops out at 7 kW AC will only yield 7 kW.
• Maximum DC charge rate: set by the battery management system. This determines how fast you can use a rapid or ultra-rapid charger.

Both limits are listed in your car's manual and are usually available from the manufacturer's website. The charger will always negotiate to the lower of its own output and your car's limit, so you will never damage the battery by using a higher-rated charger than your car can handle.

What do CCS, CHAdeMO, and Type 2 mean on the connector?

These are connector standards, and they determine whether a charger is physically compatible with your car.

• Type 2: the standard AC connector for the vast majority of EVs sold in the UK and Europe. Used for slow and fast AC charging. If you need a cable for a public AC charger, this is usually what you need. Browse our Type 2 charging cables for compatible options.
• CCS (Combined Charging System): the dominant DC rapid charging standard for new EVs. It adds two DC pins below the Type 2 inlet. Most new EVs sold in the UK use CCS.
• CHAdeMO: an older DC standard used by some Japanese-market models. Fewer CHAdeMO chargers are being installed now, and the standard is declining in the UK.

If you are unsure which connector your car uses, our charging cable finder makes it straightforward to check.

Why does my charging speed slow down when the battery is nearly full?

Lithium-ion batteries accept charge fastest when the state of charge is between roughly 20% and 80%. As the battery approaches full, the battery management system deliberately reduces the charge rate to protect cell health and prevent overheating. This is called the charging curve, and it is the main reason that the estimated time remaining on a charger can increase steeply in the final 20% of a session. At public rapid chargers, this effect means it is often more efficient to charge to 80% and then drive to your destination or the next charger rather than waiting for a full charge.

Does a higher-rated charger cost more to use?

Most public networks price by the kilowatt-hour (kWh) of energy delivered, regardless of the charger's power rating, but some networks also apply a connection fee or a per-minute rate. A higher-rated charger finishes the session faster, which reduces any per-minute costs, but the cost per kWh is usually the same across the network. Always check the pricing information displayed on the charger screen or in the network's app before you start a session: pricing structures vary between networks and can change. Never assume the rate from one visit applies to the next.

Frequently asked questions

What does kW mean on a public charger?

kW stands for kilowatts and measures the rate at which the charger can deliver electricity to your car. A higher kW rating means faster charging. The speed you actually experience depends on both the charger's rating and your car's maximum accepted charge rate: the car and charger negotiate to the lower of the two.

Is a 50 kW charger fast enough for a long motorway stop?

For most EVs, a 50 kW rapid charger can add a useful amount of range in 20 to 40 minutes, depending on battery size and how much the battery is already charged. It is typically adequate for a comfort break but slower than ultra-rapid options at 100 kW or above. Check your car's DC charge rate to know what to expect.

Can I use an ultra-rapid charger if my car only accepts 50 kW DC?

Yes. The charger and car negotiate automatically, and the session will run at your car's maximum DC rate, not the charger's maximum output. You will not get more speed than your car can accept, but you will not damage anything. Ultra-rapid chargers are compatible with lower-rated cars.

Why does the charging speed drop near the end of a session?

This is normal. Lithium-ion batteries accept charge most quickly between around 20% and 80% state of charge. As the battery fills, the battery management system reduces the rate to protect cell health. For rapid charging stops, aiming for 80% and then driving on is usually more time-efficient than waiting for a full charge.

What connector do I need for a public rapid charger?

Most new EVs in the UK use CCS for DC rapid charging. The cable is tethered at the charger, so you do not need to bring your own for DC rapid or ultra-rapid sessions. For AC chargers, you usually need a Type 2 cable, which may or may not be tethered depending on the installation. Check the charger listing or network app before you arrive.

How do I find out my car's maximum charge rate?

Your car's owner's manual lists both the maximum AC and maximum DC charge rates. The manufacturer's website usually includes this information in the technical specifications. Some EV comparison tools and apps also list these figures. Knowing both rates before a long journey helps you plan stops more accurately.

Reading a charger's power rating is straightforward once you know your car's own limits. Check your onboard AC rate and maximum DC rate before your next long trip, confirm the connector type you need, and use the network's app to see live pricing before you plug in. For home charging or backup on the road, browse our range of portable EV chargers, and visit our guides index for more practical EV charging advice.