Electric car charging explained: What all the jargon means
Electric car charging comes with a long list of technical terms, from ‘kW‘and ‘kWh’ to ‘CCS‘, ‘AC‘, ‘DC‘ and ‘preconditioning‘. Here’s what they all mean in plain English – and what you actually need to know when you’re choosing and charging an EV.
Charging an electric car is really quite simple: you plug the car into a suitable charger and electricity flows into the battery. Understanding all the terminology surrounding it, however, can be considerably less straightforward.
Look through the specifications of a new electric car and you might see a ’77kWh battery, 11kW AC charging, 150kW DC charging and a 10% to 80% charging time of 28 minutes’. Then there are Type 2 and CCS connectors, charging curves, preconditioning, tethered cables, smart charging and an expanding collection of other terms to get your head around.
Fortunately, you don’t need an electrical engineering degree to understand any of this. Most EV charging jargon describes either how much electricity the battery holds, how quickly it can be charged or how you connect the car to a charger. So let’s translate it into plain English.
A quick glossary
A measure of energy – how much electricity the battery can store or how much you’ve added when charging. Electricity is usually priced per kWh.
A measure of power – essentially how quickly electricity can be delivered to the car. A higher kW figure means potentially faster charging.
The electricity supplied by the grid. When using an AC charger, the car’s on-board charger converts the electricity to DC before it reaches the battery. Commonly used for home, workplace and slower public charging.
The type of electricity stored by the car’s battery. DC rapid chargers convert electricity before supplying it directly to the car’s battery, allowing much higher charging rates than AC charging.
This is the maximum power a charger can potentially provide, shown in kW. Common examples include 7kW, 11kW, 50kW, 150kW and 350kW. Your car may charge more slowly depending on what it can accept, how full the battery is, the battery’s temperature and other factors.
The way an EV’s charging speed changes as its battery fills. Charging doesn’t happen at one constant rate, so the maximum kW figure doesn’t tell you the whole story.
How long it takes to charge the battery from 10% to 80%. This is commonly used to demonstrate rapid-charging performance because charging generally slows considerably as the battery approaches full.
Heating or cooling the battery before rapid charging to bring it to a suitable temperature. This can allow the battery to accept higher charging rates, particularly in cold weather.
The standard connector used for AC charging by modern electric cars in the UK and Europe. Commonly used for home, workplace and public AC charging.
The standard connector used for DC rapid charging by most modern electric cars in the UK and Europe.
An older DC rapid-charging connector mainly found on some older Japanese EVs, such as previous generations of the Nissan Leaf.
What’s the difference between kW and kWh?
A kilowatt (kW) is a measure of power. In EV charging terms, it tells you how quickly electricity can potentially be delivered to the car.
A kilowatt-hour (kWh) is a measure of energy. It’s used to describe how much energy a battery can store and how much electricity you’ve consumed when charging.
An easy analogy is filling a petrol tank. kW is roughly equivalent to how quickly fuel is flowing through the pump, while kWh is how much fuel you’ve put into the tank. So an electric car might have a 60kWh battery but be capable of charging at a maximum of 150kW. Electricity for charging is also usually priced per kWh. If you put 50kWh of electricity into a car at 30p per kWh, for example, the electricity would cost £15.
kW vs kWh
kW = how quickly you can charge
kWh = how much energy you’re putting into the battery
A higher kW number means potentially faster charging. A larger kWh battery generally contains more energy, although that doesn’t automatically mean a longer driving range.
What’s the difference between AC and DC charging?
Electric cars can be charged using either alternating current (AC) or direct current (DC). The electricity supplied by the grid is AC, while an electric car’s battery stores energy as DC. When you use an AC charger, the electricity therefore has to be converted from AC to DC before it can be stored in the battery. This conversion is carried out by the car’s on-board charger.
That’s why the car itself determines how quickly it can accept AC power. A public charger might be capable of supplying 22kW, for example, but if your car has an 11kW on-board charger it will only take up to 11kW.
With DC charging, the conversion takes place outside the car and DC electricity is supplied directly to the battery system. This allows much faster charging rates and is why rapid public chargers use DC.
What do 7kW, 11kW, 50kW and 150kW actually mean?
These numbers describe the maximum power a charger can potentially provide. A typical UK home wallbox offers around 7kW AC, while some cars and suitable electrical installations can support 11kW AC. You’ll also encounter 22kW AC chargers at some public and destination locations.
Public DC chargers are considerably more powerful. Depending on the site, you might find anything from 50kW to 350kW or more.
The Department for Transport currently divides public chargers into the following categories: ‘standard’ from 3kW to less than 8kW, ‘standard plus’ from 8kW to less than 50kW, ‘rapid’ from 50kW to less than 150kW and ‘ultra-rapid’ at 150kW or more. Other organisations and charging networks may use slightly different terminology.
For that reason, we’d concentrate on the actual kW figure rather than getting too hung up on whether a particular operator describes a charger as ‘fast’, ‘rapid’ or ‘ultra-rapid’.
As a very rough guide:
| Charger output | Where you might find it | Typical use |
|---|---|---|
| 2–3kW | Three-pin socket | Occasional/very slow charging |
| 7kW | Home, workplace, street | Overnight charging |
| 11–22kW | Workplace/destination/public | Faster AC charging |
| 50–149kW | Public charging sites | Rapid DC charging |
| 150kW+ | Motorway services/charging hubs | Ultra-rapid DC charging |
But there’s an important catch: the number written on the charger doesn’t tell you how quickly your particular car will charge.
Why won’t my electric car charge at the charger’s advertised speed?
If you plug a car capable of 100kW charging into a 350kW charger, you won’t suddenly get 350kW. The maximum charging rate is determined by whichever part of the system is the limiting factor.
That includes how much power the charger can provide, the maximum rate the car can accept, how full the battery already is, battery temperature, the car’s charging software and conditions at the charging site.
So if your car has a maximum DC charging rate of 130kW, that’s the most it can take even from a 350kW charger. And even then, you won’t necessarily see 130kW throughout the charging session. That’s where the charging curve comes in.
What is a charging curve?
An electric car’s battery doesn’t generally charge at one constant rate from empty to full. Instead, the charging speed rises and falls throughout the session. Plot that charging rate on a graph and you get what’s known as a charging curve.
The car may build towards its maximum charging rate shortly after you plug in and then hold a high rate for a period before gradually slowing down as the battery becomes fuller.
How long it can sustain a high charging rate is just as important as the headline peak. For example, a car that briefly reaches a 250kW charging peak may not complete a charging stop any faster than another car that peaks at 200kW but maintains close to that rate for much longer.
Don’t judge an EV by its peak charging speed alone
A 250kW car isn’t automatically quicker to charge than a 200kW car. Look at the manufacturer’s 10% to 80% charging time as well. It gives you a better indication of how long you’re likely to spend at a rapid charger on a long journey.
Why do manufacturers quote 10% to 80% charging times?
You’ll often see an EV advertised as ‘charging from 10% to 80% in 25 minutes’, or something similar.
Why not quote 0% to 100%? Partly because rapid charging becomes considerably slower as a battery approaches full charge. This is deliberate and helps protect the battery. The 10% to 80% period therefore gives a more useful indication of the car’s rapid-charging performance.
There’s nothing special about 80% that means you have to unplug at that point. You can continue to 90% or 100% if you need the additional range. But on a long journey, you may find that the charging rate is slower after the 80% mark, and it can be quicker overall to continue driving and stop at another rapid charger later rather than wait for the final 20%.
What is battery preconditioning?
Battery temperature can have a big effect on rapid-charging performance. Electric car batteries have a preferred temperature range in which they can accept high levels of power. If the battery is very cold, the car may substantially limit its charging rate.
Battery preconditioning prepares the battery before you reach a rapid charger, usually by heating it to a suitable temperature. Depending on the car and conditions, the system may also manage cooling. Some electric cars allow preconditioning to be switched on manually. Others do it automatically when you enter a compatible rapid charger as your destination in the car’s navigation system.
This is one reason a driver might plug into a 150kW charger on a cold winter morning and initially receive nothing like 150kW.
What are Type 2, CCS and CHAdeMO?
These are different types of charging connector. For most modern electric cars sold in the UK, there are two you really need to know about.
‘Type 2’ is the standard connection you’ll normally use for AC charging. That’s what you’ll typically find on a home wallbox or many destination chargers.
‘CCS’, or Combined Charging System, is the standard connection used for DC rapid charging on most modern UK and European electric cars. A CCS connection effectively expands the Type 2 design with additional connections for high-power DC charging.
You could also encounter ‘CHAdeMO’, particularly on older Japanese electric cars such as previous generations of the Nissan Leaf. It has become much less relevant to new-car buyers as CCS has become the dominant European standard.
What does tethered or untethered mean?
This simply tells you whether the charging cable is permanently attached to the charger. A tethered charger has its own cable. You park, unwind the cable and plug it into the car. An untethered charger has a socket instead, so you need to bring your own charging cable.
DC rapid chargers are tethered because their high-power cables are considerably heavier and form part of the charging equipment.
At home, either arrangement is possible. A tethered wallbox is generally more convenient because the cable is always ready to use. An untethered unit can look tidier when it isn’t in use and allows the cable to be removed or replaced separately. There’s no meaningful difference to the car once its plugged in.
Can I charge an electric car from a normal plug socket?
Yes, most EVs can be charged from a conventional domestic three-pin socket using the appropriate charging cable.
But it’s very slow. A domestic socket will generally provide somewhere around 2–3kW, compared with roughly 7kW from a typical dedicated home wallbox. For a small battery or occasional emergency use, that may be sufficient. Charging a larger-battery EV from low to full could take well over 24 hours.
More importantly, EV charging places a sustained electrical load on the socket for many hours. Regular home charging is therefore better handled by a properly installed dedicated EV charge point. Don’t use extension leads or improvised electrical arrangements unless specifically approved for the equipment involved.
What is smart charging?
A smart charger can communicate with other systems and control when your EV charges instead of simply supplying power whenever you plug it in.
For most owners, the most useful feature is scheduled charging. If your electricity tariff is cheaper overnight, for example, you can plug the car in when you get home but tell it not to start charging until the cheaper period begins.
Depending on the charger and energy provider, smart systems may also adjust charging according to electricity demand, energy prices or available solar generation.
Another related feature is ‘load balancing’. This monitors electricity demand within the home and can temporarily reduce the car’s charging rate if other high-power appliances are being used, helping to prevent the property from exceeding its available electrical capacity.
What’s an RFID card?
RFID stands for ‘radio-frequency identification’. It is a contactless card or fob linked to a charging account. Hold it against a compatible charger and the network recognises your account, allowing you to start or stop a charging session and bill the electricity accordingly.
They’re still useful if you frequently use particular charging networks, and roaming services can allow a single RFID card to work across several networks.
But for occasional public charging, increasingly widespread contactless bank-card payment means carrying a collection of separate network cards is much less necessary than it once was.
What are V2L, V2H and V2G?
These terms refer to bidirectional charging, where electricity can flow out of the car as well as into it.
V2L – vehicle-to-load: Allows the car’s battery to power electrical appliances or devices. Depending on the car, this could mean plugging equipment into a socket inside the vehicle or using an adaptor connected to its charging port.
V2H – vehicle-to-home: Allows energy stored in the car’s battery to be used to supply electricity to a home.
V2G – vehicle-to-grid: Allows electricity from the car’s battery to be returned to the wider electricity grid.
V2L is already offered on a growing number of electric cars, while V2H and V2G are more complicated because they require compatible cars, charging equipment and energy systems. Simply owning an EV and a home charger doesn’t automatically mean you can send electricity back into your house or the grid.
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This article was originally published in June 2022, and was updated in August 2026.
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