Home EV charging explained: from wallboxes 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.

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While debates rage about the roll-out, speed 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 wallbox?

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.

(Photo: Jaguar)

Types of charger

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

Speed

All home wallboxes 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, 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 wallbox cuts this to just under seven hours, while a 22kW unit will take just over two hours.

Tethered or untethered

Wallboxes are sold as tethered or untethered. Tethered come 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 wallboxes 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.

(Photo: ev.engery)

How much do home chargers cost?

The price of a home wallbox 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.

Prices start at around £700-£800, rising to well over £1,000 but those are before the government grant or any offers from a car maker. The standard government grant (see below) brings basic units down to around £450-£500.

Tethered units are usually more expensive than untethered, 7kW will cost more than 3kW and sleeker designs can cost more. Smart chargers appear more expensive than “dumb” ones on paper but are they 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 car makers also offer a contribution towards the cost or will supply a free wallbox to buyers of their EVs.

EV charger grants

To encourage uptake of EVs, the UK Government offers a grant towards the installation of a wallbox via the Office of Zero Emission Vehicles (OZEV).

The Electric Vehicle Homecharge Scheme (EVHS) will pay 75 per cent of the cost of a wallbox and installation, up to a maximum of £350.

You can check car eligibility, approved chargers and installers and apply for the grant on the Government website here.

In Scotland, the Energy Saving Trust will provide up to £300 further funding on top of this, with an additional £100 available for those in the most remote parts of Scotland.

How much does home charging cost?

(Photo: Jaguar)

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 Renualt 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 car makers, 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 to 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 wallbox 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 wallbox.

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. Some such as PodPoint or BP Pulse are linked to major energy or fuel firms; some such as Rolec, work in domestic, public and industrial settings while others such as Andersen and Zappi focus on home units. Who you go for comes down to your specific needs in terms of features, design and price.

Likewise, there are plenty of independent installers to choose from, although your wallbox supplier may have a preferred installation firm. Just make sure whoever you use is on the Government’s list of authorised fitters.

Once you’ve chosen a supplier, you need to confirm with them which units are suitable. Jake Hudson from Rolec, who supplied our unit, explained: “Although drivers will always wish for their vehicle to be charged as quickly as possible with a superfast charger - 11kW or 22kW - sometimes this may not be possible.

“When choosing a chargepoint, drivers will need to understand whether their property’s power supply will meet with the demands of the chargepoint and the vehicle. The majority of households in the UK are fed with a single phase supply which would put the superfast units out of reach. This is also why we ensure that all of our customers receive a survey and site check before finalising on the charge point.”

The next decision is tethered or untethered - we went untethered as the test cars I’ll be driving usually come with their own cables - and, in our case, choosing a colour. Many manufacturers, including Rolec, are making an effort to make their charger more attractive through design and colour. Allowing the kids to get involved means I ended up with a “terracotta” box which looked vivid orange on-screen but turned out to be a more muted plant pot shade.

All that done, it’s a matter of placing the order and arranging the installation.

Normally, the installer would carry out a site visit to assess the work but in these Covid-affected times I was instead asked to send in photographs of the key areas. It sounds potentially confusing but I was sent a simple list of required images - the main fuse, main electric switchboard, where I wanted the charger fitted and the route from there back to the main fuse.

Stewart Dickson from our installer, Jorro, told me that in most cases this is enough for them to gain a basic understanding of the work required but if homeowners are in any doubt, installers are still happy to carry out a site visit before starting work.

The average installation time is around three ours and thankfully, our planned location and cable route was straightforward but Stewart explained that some factors can have an impact on the time an installation takes and potentially the cost.

He told me: “The main things that can cause issues are the location of the fusebox/consumer unit and the main fuse rating that the property has. If the fusebox is under the stairs in a modern new-build, then the cable route tends to have to go upwards to the loft and then back out to the external wall that way, this means more labour time and adds cost for materials. Older properties have underfloor access for the cable, but newer buildings, sadly, have concrete flush floors and/or laminated floors that can’t be touched.

“The other thing, which causes delays more than anything, is the main fuse rating. They are always 60,80 or 100amps in capacity and, depending on the house load, it can be necessary to upgrade before we can fit a 32A charger. Only the owner of the cable supplying the property can carry out the upgrades and that is the power distribution network. This sometimes comes at an extra cost to the customer, of no more than £300 and the timeline is anywhere between three and eight weeks.”

After a relatively short wait for the unit to arrive from the factory our installers turned up and got to work. As soon as they arrived, they spotted a tidier route to run the cable - showing that while photos are fine there’s no replacement for experience and the benefits of an advance site visit.

The fitting process involved running a new heavy-duty cable from the charger unit to the main fuse and the main household switchboard. Some chargers, including ours, also require an external earth rod located near the charger.

In some instances you’ll be able to have all the cabling routed internally, through walls or under floors, but for us that wasn’t an option. That meant some noise and dust as a couple of neat holes were drilled through the exterior wall of the house and the garage but most of the work didn’t cause any disruption. Obviously, if you’re running cables under floors and through the house, expect a bit more inconvenience.

Contrary to my fears, the household power supply only needed to be interrupted briefly when the final run of cabling was connected to the main fuse board. Ours was out for around 10 minutes and, all told, the whole installation took less than three hours. Externally the only evidence of the work is one cable neatly run near ground level at the front of the house, the external earth cable and the slim charging unit itself. Inside, some well hidden trunking in the fuse cupboard and along the garage wall are the only giveaways.

With the hardware installed, the final step was to install the ev.energy app which allows live monitoring and management of the charger and plug in our Volvo XC60 hybrid test car. The app works with multiple brands of charger and vehicle and allows you to  track live and historic charging data and costs. Using information such as your vehicle, energy supplier and regular start times, it can also be used to manage your charging schedule to get the cheapest top-up.

Before I started the process, I imagined that having a home charger installed would be complex and time consuming but in reality, all it took was a little research into the right charger for me, sending a few photos and one morning of minor disruption. And now I'm all set to embrace the future. Unless there's a sudden lurch towards hydrogen...