One of the most common questions we hear from prospective EV buyers is how long will it take to charge an electric car?
With old petrol/diesel vehicles, the variables are small – given that most pumps deliver fuel at the same speed, into a tank that's roughly the same size as the next car. It might take a minute more if the tank was completely empty, but – overall – it's a predictable experience that we're all familiar with.
With an EV, the list of variables is longer and some of them are interconnected. These include:-
- Are you choosing AC or DC?
- What speed is your EVs internal charging mechanism?
- How fast is the charger you're connecting to?
- What's the size of your battery?
- How full is that battery?
Also, in order to charge in public at all, you'll need access to a charging station. On the plus side, the UK network has been growing and evolving quickly. Over the last six years, the charge point network has grown from 6,500 to more than 32,500 chargers as of June 2022. Of these, over 22,500 devices are fast or rapid chargers. The speeds are increasing too, with 350kW chargers starting to arrive.
The Government recently kicked off a £1.6 billion investment programme to make that network much stronger by 2030. It's clear that we're living in the last generation of EV drivers that will need to think about charger locations and recharging speeds.
Charging at home or at the office will generally involve an AC charger – while public chargers are increasingly becoming DC.
Most electric cars require a direct current (DC) internally, but charging at home using a domestic socket provides alternating current (AC) which is converted to DC by the vehicle. Rapid DC chargers do this conversion before the current reaches the vehicle which speeds up the charge time.
Slow AC Charging
Slow AC chargers are rated from 2.3kW to 6kW depending on the home or lamp post charger. While this will recharge a typical electric car in eight to twelve hours, it is ideal for home use to charge the car overnight or at the workplace.
The lowest level will be “granny” chargers that plug into a regular 13a plug and therefore won't be able to deliver more than 3kW, although most are below 13a to avoid overpowering home wiring so deliver less.
The advantage of using a slow charger is that it keeps the car’s battery healthy as it produces less heat. It is also pocket friendly as some public slow chargers are free or heavily subsidised, and otherwise rates are not much more than a domestic electric supply, such as Ubitricity lamppost chargers.
You will find that 7kW chargers are popular at home (to fill your EV overnight) or as cheap/free top up charging options – for example at supermarkets, leisure centres and car parks.
“Fast” AC Charging
Fast AC chargers are the most common connectors in the UK, accounting for more than 50% of the charging network. Technically, 7kW wallboxes are included in this category, but they're not much faster than AC chargers in the “Slow” category.
The truly faster AC supplies range from 11kW to 43kW, so they can reduce the charging time by up to ten times when compared to a slow charger.
While charging times can vary depending on the connector and the car, an 11kW charger will fully charge a typical car in four to six hours whereas a 22kW charger can deliver the same in two to three hours. Very few cars support charging at 22kW and even fewer at 43kW.
Rapid and Ultra-rapid DC Charging
The fastest way to charge an electric car is using a modern DC charger. With the right EV, you can get from 10% right up to 80% in as little as 20 minutes.
The slower DC chargers offer a 50kW charge – which can deliver as much power in one hour as a 7kW charger can in 7 hours. Worth thinking about if you are in a hurry. Below 100kW, DC chargers tend to be called “Rapid”, although in the USA they tend to use the word “Fast” for this category, just confuse things further.
Above that the word usually used (in the UK) is “Ultra-rapid”, referring to chargers that can deliver 100kW or more.
Most EVs can take advantage of Ultra-rapid chargers that can deliver 100-150kW.
Only the latest cars are likely to be equipped for really fast Ultra-rapid charging – ranging from 200-350kW.
The Charging Curve
Another important thing to be aware of, is that each battery has a ‘charging curve'. When it is nearly empty, it will accept a very fast charge – potentially filling up at the fastest speed available. However, when it gets close to 80%, it will slow right down. This is to protect the long-term health of the battery.
You can visualise this process when you think of pouring a cup of coffee. You pour really quickly into an empty cup, but slow down when it's nearly full. We advise that you only sit on a public charger past 80% if you absolutely must. The last 10-20% will take much longer and could affect the long term health of your battery.
Batteries will tend to accept a charge faster when they are warm. Some cars will even have a pre-heating cycle that kicks in when you tell the onboard sat-nav that your destination is a charging station.
While the rapid and ultra-rapid charging network has grown by almost 50% since 2020 (there are currently over 6,000 rapid and ultra-rapid chargers in the UK) it is also worth noting that relying entirely on rapid charging does have the potential to degrade the battery. Despite the fact that modern EVs can keep their batteries cool, the quick heating of the battery over time may decrease the driving range or increase the charge time of the car.