How to charge your electric car with solar panels

Solar panels generate free, clean electricity – so naturally, you’ll want to use it to power everything in your life.

Charging your electric vehicle with solar electricity can save you hundreds of pounds, slash your carbon footprint, and reduce your dependence on public charging stations and the grid.

In this guide, we’ll explain how using solar panels to charge an electric car works, what the best setup is, how much it costs upfront, and how much you can save.

To find out how much a solar & battery system could save you in the long run, answer a few quick questions below and we'll generate an estimate.

Can you use solar panels to charge an electric car?

You can absolutely use solar panels to charge an electric car.

Your solar panels will come with an inverter that converts the DC (Direct Current) electricity that comes from the sun to AC (Alternating Current) electricity, which you can use in your home and to charge your car.

So once you’ve bought your solar panel system and EV, you can technically plug your car into a wall socket – but that would be slow, inefficient, and potentially hazardous.

Instead, you should get an EV charger, which will use solar electricity to replenish your car’s battery as it’s being generated by your panels.

Unless you have a particularly large solar panel system, your charger will usually combine the solar energy you generate with electricity from the grid, to reach its standard output level.

Alternatively, you could buy a solar-compatible charger, which allows you to choose when you charge your car, and use exclusively solar electricity when you do so.

This works even more productively when combined with a solar battery, which enables you to store your solar energy up during the day, then charge your car at night.

How does it work?

If you buy an EV charger that isn’t fully compatible with solar panels, it will still use the electricity your panels generate, either while it’s being produced or from your solar battery, if you have one.

However, you won’t be able to control what source your charger uses; it’ll simply draw electricity from wherever it can.

That means it’ll probably use some grid electricity if you charge your car during the day, to meet the peak power rating of your EV charger.

You could also buy a technologically advanced ‘solar charger,’ which allows you to charge your car with solar electricity more effectively, with more options.

These chargers usually come with a CT (Current Transformer) clamp that automatically turns the charger on when it senses your solar panels are generating electricity.

The rest of the time, your charger either won’t fill your car’s battery at all, or will do so using grid electricity – but relatively slowly.

When compared to a regular EV charger, a solar charger can significantly increase how much of your solar electricity you use to charge your car.

This will allow you to cut your electricity bills, and ensure your EV is always sufficiently charged.

Which EV chargers are solar compatible?

At this stage in their technological development, it’s relatively easy to find solar-compatible EV chargers.

Here’s a rundown of all the models you can currently use to efficiently charge your EV.

Does a storage battery help with EV charging?

A storage battery helps with EV charging by storing solar electricity so you can use it to charge your car after the sun goes down.

Without a storage battery, your solar panels can only charge your EV when they’re producing electricity, during the day.

And if your solar panel system produces a lower output than your EV charger – for instance, if it’s a 4 kWp (kilowatt-peak) array powering a 7 kW charger – you’ll still use some grid electricity alongside your solar energy.

And you won’t be able to use any solar electricity in this process if your car’s not usually home when the sun’s up – which is the case for at least some of the year if, for instance, you’re among the 68% of Brits who drive to work.

If you wait until the sun’s gone down, your home charger can only use grid electricity to fill up your EV – a process that typically costs £581 per year, according to our calculations – instead of free solar electricity.

The only way to effectively use solar panels to charge an electric car that’s not home during the day is by using them alongside a storage battery.

How many solar panels do you need to charge an electric car?

On average, you need six solar panels to charge an electric car – assuming each panel has a peak rating of 400 W.

However, the average three-bedroom household that’s looking to power its appliances and charge an EV will need a 5.9 kWp system, which is 14 solar panels at 400 W each.

How much does it cost to charge an electric car with solar panels?

It costs £14,500 to install a solar panel system and home charging point that can charge your electric car with solar panels.

First, you need a 5.9 kWp solar panel system, which typically costs around £11,500. If you add a solar battery, allowing you to store your solar electricity and use more of it to charge your car, the price tag rises by £2,000.

You’ll also need a home charger, as you can’t efficiently use solar electricity to power your car without one. These typically cost around £1,000, for an overall cost of £14,500.

The average EV needs 2,029 kWh per year, which this system will produce – and thanks to the solar battery, you’ll be able to use it whether your car is home during the day or not.

However, due to seasonal variations in the amount of light that hits your solar panels, this supply of solar electricity isn’t consistent.

You’ll therefore need to import around half of your electricity from the grid in winter, plus a small amount during autumn, according to our calculations.

The good news is you’ll typically generate more than you need in order to charge your EV in spring and summer, which you can use in your home, cutting your electricity bills further.

This means even if you already have a home charger, solar panels will still save you £594 on average per year, or 102% of your EV charging bill.

If you don’t already own a home charger and use public chargers to top up your car’s battery, this setup will save you £1,040 per year, on average – allowing you to break even in 11 years, at February 2024 prices.

What are the pros and cons of charging an electric car with solar panels?

There are several pros – and not many cons – of charging an electric car with solar panels.

After all, once you’ve bought the system and charger, you can generate free, clean electricity to power your car.

When is the best time to charge an electric car with solar panels?

The best time to charge an electric car with electricity from your solar panels is around the middle of the day, when the sun is highest in the sky and your system is generating the most energy.

This is often the point when your panels are generating more electricity than you can use, so instead of sending it to the grid through one of the best export tariffs, you can use it to charge your car.

However, if you have a solar battery, you can store this electricity to use in the evening or night, meaning your car doesn’t have to be home during the day to be charged.

If you’re on a smart charging tariff like Intelligent Octopus Go and you need to top-up your car’s battery further, you can then charge your car from the national grid for just 7.5p per kWh, any time between 11:30pm and 5:30am.

How long does it take?

It takes around six hours to charge the average electric vehicle from 20% to 80%, using a standard 7 kW charger.

It’s usually best to charge your car to no more than 80%, both to lengthen your battery’s lifespan and because it takes roughly the same amount of time to charge up to 80% as it does to charge from 80% to 100%.

You can absolutely charge your car to 100%, but it’ll degrade the battery slightly every time you do, so it’s best to only do so before a long trip. When you do so, it’ll take around 10 hours.

There’s also no harm in discharging your electric vehicle below 20% – as long as you don’t leave it that way for weeks or months – but it’s always safer to have some electricity left in your battery, just in case.

If you’re using a solar charger, it’ll automatically charge your car’s battery when your solar panels are generating electricity, and use grid electricity the rest of the time – but more slowly.

This means it could take longer to charge your car, especially during winter when your panels are less productive.

What’s the best tariff for solar EV charging?

The best tariff for solar EV charging is usually Intelligent Octopus Go.

Between 11:30pm and 5:30am each day, it offers a low import rate of 7.5p per kWh for both your EV and domestic electricity consumption.

You can also use it alongside the Octopus Outgoing export tariff, which offers either a generous fixed rate of 15p per kWh or a variable rate.

If you use a sizable proportion of the electricity your solar panels generate, and consume less than 5,000 kWh of electricity per year – as the majority of UK households do, even with an EV – this is the tariff for you.

However, if you export an unusually large amount of your solar electricity and use more than 5,000 kWh per year, you may be better off on Intelligent Octopus Flux.

This tariff allows you to export solar electricity for an above-market rate during a peak period between 4pm and 7pm.

You may also want to look into Octopus Power Pack, a pioneering vehicle-to-grid tariff that allows you to store electricity in your car’s battery, then export it to the grid when it’s most profitable to you.

It’s currently only available to households with a Wallbox Quasar charger and one of the following cars: the Nissan Leaf, Nissan e-NV200, and Mitsubishi Outlander PHEV.

How much greener is it to charge an EV with solar?

You’ll save 248 kg of CO2 per year by charging an EV with solar energy instead of grid electricity, on average.

Electricity from the national grid is considerably greener than it used to be, but it still emits 149 g of CO2 per kWh.

The average EV owner requires 2,029 kWh to power their annual driving distance of 6,600 miles, around 82% of which can typically be supplied with solar panels, according to our calculations.

Due to seasonal variations in amounts of daylight, the remaining 18% will typically be supplied by the grid. You can power your car with 100% solar electricity, but it’ll require an inefficient, oversized system.

Your appropriately sized solar panel system will still likely produce excess electricity during the summer and spring, which you can use at home or sell to the grid.

Either way, it’ll reduce your carbon footprint even further.

Summary

You now have all the information you need to decide whether or not you want to use solar panels to cut hundreds of pounds off your annual EV charging costs.

All that’s left is to choose a solar panel system – and ideally, a solar-compatible EV charger to go with it.

If you’re wondering how much a solar & battery system could save you, just click the button below, answer a few questions, and we’ll provide you with an estimate.

Charging an EV with solar: FAQs