Your questions answered

Can solar panels charge an electric car?

Using solar panels to charge your electric car can save you money in the long run. Here’s everything you need to know about charging an electric car with solar panels

Solar Panels

Electric cars are favoured for their reduced environmental impact compared  to cars with a combustion engine. One of their main benefits is that they don't have an engine or exhaust, so no toxic emissions are produced. However, the source of the electricity used to charge an EV and the methods used to generate it are limiting factors that can hinder climate-friendly driving.

For example, if an electric car is charged with power from the UK national grid, some of that electricity may have been generated using fossil fuels. While the UK government is trying to reduce the National Grid’s reliance on fossil fuels, gas and coal are still necessary to generate enough electricity for the nation. 

If you're determined to source emissions-free energy for your electric or plug-in hybrid car, there are ways to do so, while saving money in the process. You can ensure that the electricity used for charging comes from renewable sources with a specific tariff, or you can generate your own energy. One way of doing the latter is to build your own solar-powered EV charging station and use solar panels to charge your electric car.

Solar panels for EV charging

Installing solar panels on the roof of your house is a great way to generate your own power for charging an EV. While the amount of solar panels needed to charge an EV depends on the size of the car's battery, about 10 panels should generate enough electricity to charge a car with an average-sized battery.

It’s important to remember that the solar panels cannot store electricity themselves, meaning whatever the panels generate must be used immediately by devices plugged in at home, or else it'll be returned to the grid.

Building a solar-powered EV charging station

Thankfully, there are additional pieces of equipment that can help you make the most of the electricity generated by solar panels. Solar power can be stored in a solar battery, which is a device offered by a number of providers including e.on, EDF, Moixa and Tesla. The benefit of a battery system is that any excess energy from your solar panels can be stored and used to power your home or electric car when the panels aren't producing charge overnight. Otherwise, your solar panels will only be able to charge your electric car during the day.

To efficiently charge an electric vehicle using solar panels, you will also have to install a home charging unit and a PV inverter unit that converts the solar energy into DC current for the vehicle. There are several of these systems available for purchase already, some of which combine both of these elements in one box. However, there's no standalone solar-powered charging system available – rather, it must be integrated with the rest of your domestic power supply system.

These systems don’t come cheap, though. Depending on which wallbox you buy, prices range from a couple of hundred pounds for the most basic 3kW systems, rising to close to four figures for the most advanced 22kW units. Solar panels are expensive, too. A 1kW system with four panels taking up eight square metres costs between £1,500 and £3,000. Bigger systems cost more.

A 1kW system is estimated to generate 850kWh of energy output a year: that could fully charge the new Honda e 24 times over, which translates into some 3,250 miles of driving range. If your annual mileage is relatively low, solar panels could be a great long-term solution. It's worth noting, however, that the average domestic solar-panel installation doesn't produce enough electricity in a day to fully charge an electric car.

How long does it take to charge an electric car using solar power and what are the savings?

This obviously depends on the amount of sunlight and the type of panels on your roof, as well as the type of wallbox charger you have. We visited one electric-car owner, Warren Philips of Shoreham-on-Sea, who uses solar panels to charge his Renault ZOE. On a sunny day, the panels on his roof can generate upwards of 40kWh of electricity, enough to charge the 40kWh battery in his car.

Most electric-car charging at home happens overnight, when there’s no sun to generate free electricity. This is why it’s worth considering installing a home battery system – like a Tesla Powerwall (below) – to store the solar energy to recharge your car.

Telsa Powerwall battery

Tesla Powerwall battery

Tesla's system uses a 14kWh battery and can provide a charge of up to 7kW, or 5kW continuously. The battery can be mounted inside or outside, either on the floor or on a wall, while up to 10 can be installed together to increase storage capacity.

Similar, less high-end systems are available from a number of other suppliers: Moixa offers batteries in three capacities (4.8, 7.2 and 9.6kWh), while suppliers including e.on and first4solar.co.uk use GivEnergy batteries available in a range of capacities.

Again, this is another added expense, but in the long run, the savings can far outweigh the costs. Another electric-car owner we spoke with, Warren Philips, estimated that he will be £13,000 better off in 20 years' time after installing his solar panels, wallbox charger and Tesla Powerwall.

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