Electric Vehicle (EV) charging: Slow, Fast or Rapid?

There are 3 charging speeds for your electric vehicle: slow, fast and rapid.  The rapid charging point cannot be installed in the home, but both the slow and fast charging points can be.  There is also an option to upgrade the fast charger to an even faster charger, so we will look at this option as well.  Home charging is by far the cheapest option but, as will also be shown, there are ways of making even more savings.  So, without further ado, let’s have a look at the three charging speeds and their advantages and disadvantages.   

Slow Charging


The slow charge (aka granny charger) is very aptly named because depending on the size of the battery, it can take anything up to about 18 hours to charge your EV.  The charger unit itself usually comes in the form of a rather handy 3-pin plug that you simply plug into a household electrical socket. This means you can charge your vehicle from anywhere where a plug socket is available (although, if not charging at home, it would be polite to firstly ask whoever might be paying the electric bill!). 

You would not necessarily need to invest in a home charging unit if you were to buy a slow charger.  This charger operates at between 2.3 kW – 2.5 kW on alternating current (AC) drawn from the National Grid.  (Whilst all EVs operate on direct current (DC), they are fitted with converters so that AC is converted to DC). You simply plug the slow charger in and switch it on as you would a household appliance, making it very convenient and easily transportable.  Whilst these chargers are ideal for home use, however, you may not perhaps, want to spend 18 hours in work while your EV charges! 

Disadvantages of a Slow Charger


The length of time it takes for a slow charger to charge your EV is not only a disadvantage, but also presents a potential fire hazard.  As explained, this type of charger is plugged into a household socket.  Running an appliance at this wattage for such a long time can cause the socket to overheat and/or strain the circuit and cables.  So, whilst the slow charge is a cheap means of charging your EV, it is not necessarily the best.  It would, however, serve admirably as a back-up charger that you could keep in the boot. 

Fast Charging


Fast chargers are the most common form of EV charger in the UK.  They are usually dedicated home charging points, but they can also be found in public places such as supermarkets and parks. Similarly to slow chargers, the fast charger uses AC from the national grid to charge your EV.  They are rated at 7kW or there abouts and so charge much faster.  That they are physically installed also removes the risk of overloaded electrical sockets as with the slow charger.

There is the option to install a 22kW fast charger at home, but the installation can be much more complicated and costly, as I’ll explain shortly.  Suffice to say that whilst the 7kW is up to 3x faster than the slow charger, the 22kW is up to 10x faster, meaning that each charger will charge in roughly 7 hours and 2.5 hours respectively.

22kW Charger Installation


As I said earlier, to opt for a 22kW EV charger home installation will be more complicated and expensive.  Most homes operate on a single-phase electrical supply, but you would have to invest in a three-phase electrical supply unless you already had this type of connection.  To upgrade to a three-phase can be costly and take time to organise.  So, if you were considering this type of charging point, you would have to weigh up the cost of the upgrade compared to the amount of time you would save on charging and whether it would be worth it.  All in all, though, to invest in a home EV fast charging point brings convenience and savings, whether it is a 7kW or 22kW charger and there are no real disadvantages.

Rapid Charging


Rapid EV charging units can be found at motorway services.  A rapid charger uses between 43kW to 50kW and can charge an EV battery from 0% to 80% in approximately 45 minutes depending on the size of the battery. Once it has reached 80% it will slow down to protect and help preserve the battery.  It may take a further 15 minutes or so to reach 100% charge.  Whilst these are the quickest chargers and convenient as a way of charging your vehicle on long journeys, they cannot be installed at your home and nor should they be used every time you need to charge your vehicle.  This is because, unlike a slow or fast charger, the rapid charge points actually use DC to charge your EV, so could potentially harm the battery with constant use.

Home Charging is the Cheapest Option


If you choose an EV home charging point, obviously your electricity bill will increase, but when comparing this increase with the cost of petrol, you will find you are saving a considerable amount of money.  Added to this, if you shop around for a suitable electricity tariff, you will make even more savings.  Look into off-peak tariffs such as overnight when electricity is cheaper and cleaner.  Some tariffs even reward you for overnight charging.  As well as this, a smart meter could make considerable savings and there are some smart off-peak tariffs that could save you even more, such as charging in the day when the wind is up and more electricity is being created.  There are even some energy suppliers who already are offering discounted tariffs specifically for the EV owner.  So, it is worth shopping around.

In Summary


Of all three speeds the best recommendation for an EV home charging unit is a 7kW (unless you have the capacity for a 22kW charger).  A fast charger will not harm your battery as regular use of a rapid charger may do and it will be at least 3x faster than a slow charger whilst removing the risk of an overheated socket.  In terms of saving money, a simple energy price comparison and change of tariff or energy provider can make a big difference.  All you have to do is make the decision and ‘flick’ the switch.

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