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Press release 25th Apr 2022

The Scotsman – Home EV charging explained

Home EV charging explained: from wall boxes to kW and cables to costs

By 2030 all-new petrol and diesel cars will be banned and we’ll all be swanning around in electric cars. That’s the theory anyway.

Obviously, many people will still be using ICE vehicles in 10 years’ time but there’s no doubting the rise of the EV.

While debates rage about the roll-outspeed and price of public charging points, it is estimated that the average EV owner does 80 per cent of their vehicle charging at home.

So it’s important to understand that process, from the home charger hardware to the charging speeds and costs associated with home charging an EV.

Here, we break down the basics of home charging and give an insight into the process of having a system fitting.

What is a wall box?

Wallbox is the industry term for a purpose-made EV charger fitted at your home or place of work. Usually, these are fitted to the external wall of your house or garage but can also be fitted internally in a garage or mounted on a free-standing post.

The benefit of these standalone chargers is that they will charge an EV far faster than a standard domestic plug socket – up to three times faster. They are also weatherproof and a far neater solution than trailing a cable out of a garage door or window.

Types of charger

There are a few key variables when considering a wall box, chiefly, speed, tethering and whether it is “smart” or “dumb”.

All home wall boxes will use an AC supply and most will be 3kW or 7kW, referring to the speed they can charge at. A 3kW charger is referred to as a “standard” or “slow” charger, and the 7kW as a “fast” charger.

You can also get 11kW or 22kW AC charging but this requires three-phase wiring usually only found in commercial or industrial premises.

A 3kW charger will take around 17 hours to fully charge a 50kWh Renault Zoe. A 7kW wall box cuts this to just under seven hours, while a 22kW unit will take just over two hours.

Tethered or untethered

Wall boxes are sold as tethered or untethered. Tethered comes with a charging cable preinstalled. This is fine if you are only charging one EV but could potentially cause problems if you later change model. Untethered or universal wall boxes feature a Type 2 socket into which you can plug any modern AC charging cable, usually supplied with the car.

Smart chargers

Smart chargers are internet-connected units that can be monitored and controlled via a mobile app, relay charging data and take advantage of preferential energy rates.

Most modern chargers now feature smart functions after funding changes meant they were the only ones eligible for a government grant.

How much do home chargers cost?

The price of a home wall box is determined by various factors including its speed, whether it has smart features and even its design. Even where you live can have an impact on the final cost.

Tethered units are usually more expensive than untethered ones, 7kW will cost more than 3kW and sleeker designs can cost more. Smart chargers appear more expensive than “dumb” ones on paper but are the only kind eligible for the OLEV grant (see below).

Installing the charger is usually included in the price as long as you use one of the manufacturer’s recommended installers. However, if the installation is particularly complicated or you live somewhere remote, you might have to pay more.

Some carmakers also offer a contribution towards the cost or will supply a free wall box to buyers of their EVs.

How much does home charging cost?

Charging costs are determined by your home electricity tariff. The average rate in the UK is 14.4p per kWh. To fully charge a model like the 50kWh Renault Zoe at that rate it will cost around £7.20.

However, many energy companies offer EV tariffs with cheaper nighttime rates. These allow you to charge overnight for as little as 4.5p per kWh. Ovo has also just launched a smart tariff that claims to offer a 6pp KWh type-of-use tariff specifically for EVs.

Some carmakers, energy providers and charging firms also offer “free miles” to buyers. This usually takes the form of a refund on household electricity when you sign up for a particular tariff but can also take the form of free access to certain public chargers.

Can I use a regular domestic plug socket?

You can use cable fitted with a regular 13A three-pin plug to charge an EV but it’s generally recommended only as a last resort. Most manufacturers recommend you have a wall box fitted and some don’t even supply a three-pin cable as standard.

This method is referred to as trickle charging and that Renault Zoe battery will take more than 29 hours to charge, compared with seven hours on a 7kW wall box.

Having a home charger installed

Since part of my job is to test drive cars and plug-in hybrids and EVs are an ever-growing part of the landscape, I decided to have a home charger installed myself.

Most EV buyers will arrange their installation via their car’s manufacturer but if you’re buying second-hand or trying to future-proof your house, you can also have one installed independently.

There are dozens of charger makers in the UK, such as Andersen who focus on home units. Who you go for comes down to your specific needs in terms of features, design and price.