Can solar panels charge an electric car?

Since electric cars don’t have an engine producing harmful exhaust fumes, they are considered to be zero-emissions vehicles by many. However, they still have an environmental impact related to emissions in many cases, because they are charged up using the National Grid and therefore indirectly make use of fossil fuels. Thankfully, with the advancement of solar tech, it’s easier than ever to make sure your car is charged using energy from the sun instead.

Fossil fuels are still used heavily around the world to produce enough power for society to function as it does. Solar power isn’t used widely for large-scale power generation in the UK, simply because we don’t have the weather for it. Wind power is much more practical here as a renewable form of power, but solar can still be really useful especially on a more local level.

The easiest way to make sure your electric car isn’t contributing to the production of emissions at power plants is to choose a home electricity provider that only buys from renewable sources - there are plenty to choose from now. The more dedicated choice, and one that can save you money as well, is to build your own electric car charging station using solar panels. It sounds complicated but the process is getting easier all the time. Read on to find out more about charging an electric car using solar power.

Solar panels for EV charging

Solar panels can be fixed to the roof of your house to generate electricity, which can be used to charge your car. The amount of power generated depends on the available light and sunshine, but also on the number of panels you install. As a rule of thumb, around 10 panels are enough to charge an average-sized car battery, but if you have a larger EV with a big battery you may need more to generate enough power.

Solar panels generate electricity but they can’t store it unless you also install a (rather expensive) battery system into your home as well. All the power being generated can be used in your home or to charge your car - and there are apps and devices to help allocate the power from your panels - but you won’t be able to charge your car at night, for example. 

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 a Honda e roughly 24 times over the course of 12 months, which translates to 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.

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.