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Solar Panels and Electric Cars

Fancy charging your electric car with free electricity from the sun?

With solar panels installed on your roof, you can charge your electric car in the cheapest and most environmentally friendly way.

Our short guide tells you everything you need to know.

Table of Contents

  • How do Solar Panels Work?
  • Charging an Electric Car with Solar Panels
  • How Long do Solar Panels Last?
  • How Much do Solar Panels Cost?
  • What about Battery Storage?
  • Summary of Key Points
  • Solar Panel FAQs

How do Solar Panels Work?

When the sun shines on a solar panel, it generates electricity. It’s as simple as that.

The ‘DC electricity’ from the solar panels is then fed into an electrical box of tricks called an inverter which transforms it into ‘AC electricity’ that you can you use in the home or at work.

There are no moving parts and nothing to service. The panels just sit there, producing free electricity from the sun, day after day.

Do solar panels work when it's cloudy? Yes, they generate electricity even when it's cloudy, but much less than they do with direct sunlight.

Charging an Electric Car with Solar Panels

If your car is plugged into its charging point while the sun is shining on your panels, then some of that solar electricity will charge your car’s battery.

Why won’t all of the electricity form the panels charge the car? Because some of the solar electricity will go to power other electric devices that are turned on, such as computers, lights, electric radiators, etc.

A typical home solar panel system will produce about 2-3 units (kWh) of electricity an hour – when in direct sunlight – good for roughly 7-10 miles of range.

So, on average, 4 hours of solar generation would add about 28-40 miles’ range to your EV’s battery.

Depending on your daily mileage – and bearing in mind solar panels don’t produce much electricity with grey skies – you can’t rely on solar panels alone to power your electric car. You will need to top up your battery using electricity from the grid as well.

How Long do Solar Panels Last?

Solar panels should function fine for at least 25 years, gradually generating a little bit less electricity each year.

The only part of the solar panel system that typically fails is the inverter. It does all the electrical heavy-lifting.

Make sure your inverter has a product warranty of at least 10 years, and consider extensions to 15 or 20 years.

You might also need to have your solar panels cleaned from time to time, though the wet UK weather often takes care of that for you.

Benefits of Solar Panels

  • Generate clean, green electricity every day
  • No fuel cost – sunshine is free!
  • Panels are very robust, 25+ years lifetime
  • Reduce your annual electricity bill
  • Protect yourself against rising energy costs

How Much do Solar Panels Cost?

Solar panel technology has come down in price enormously over the last 10 years. Here are representative costs for having solar panel systems installed at home or at work:

Home Solar Panels

A typical home solar panel system in 2022 costs between £6,000 and £10,000. That includes all of the equipment and installation costs. At the moment, domestic solar panel installations are zero-rated for VAT.

£6,000 to £7,500 will generally get you a standard, average size solar array.

In the £7,500 to £10,000 range, you can expect a larger array and/or more technologically advanced equipment. Often longer product and performance warranties, too.

For example, if there’s a tree in front of your house that casts a shadow on the roof, then you might be recommended shade mitigation technology such as power optimisers or micro-inverters. These are more expensive than a standard solar panel installation.

Obviously you could be quoted more than £10,000, for example for larger solar arrays, more expensive brands, or if the company simply wants to make more profit.

Workplace Solar Panel Systems

If you have a big roof at work, a solar panel array will allow you to generate a significant amount of electricity each day.

This solar electricity can help charge any electric vehicles you have plugged into their charging points in the carpark, as well as power other electrical equiupment, lights, computers, etc., inside the building.

Commercial solar panel installations typically start around £15,000 + VAT for small systems. If you have a big roof – say 50m by 20m – about 500 panels would fit on and the cost might be around £170,000 + VAT.

Commercial solar electricity systems usually have a payback period of 5-7 years and a useful life of at least 25 years.

If you want complete peace of mind as a business, ask your installer to quote for extended warranties on the inverters to 20-25 years. That way you're unlikely to incur any maintenance costs for a couple of decades, except possibly panel cleaning if they get dirty.

What about Battery Storage?

In most home solar panel installations, you normally only use 30-40% of the solar electricity generated.

That means 60-70% of that precious green electricity escapes to the grid. You can be reimbursed via the Smart Export Guarantee scheme, but it's more cost-effective to use as much of the solar energy in the home as possible.

How can you do that? With battery storage. A battery allows you to soak up some of that excess solar electricity before it goes off to the grid.

Typically a solar panel system combined with battery storage allows you to capture and use about 70-80% of your solar energy. Read our dedicated Battery Storage Guide for more details.


Charging Electric Cars with Solar Energy

If you have a suitable roof, adding solar panels is a great way of powering electric vehicles with 100% green electricity.

Here are the key points:

  • Solar panels at home or work can charge your electric car
  • You will need to top up your car with grid electricity – in most situations, you can't get enough electricity from the solar panels for a full charge
  • Solar panels last a long time – usually 25 years or more
  • Some EV charging points have dedicated 'solar modes', e.g. Myenergi Zappi and Indra Smart Pro
  • Driving on solar electricity means you are always emissions-free

Solar Panel FAQs

Still got questions? Check out our Frequently Asked Questions and Answers below:

At a basic level, all electric vehicle charging points are compatible with all solar panel systems.

However, some charging points have a ‘solar mode’. If you activate it, it guarantees your car will only charge with electricity from your panels (no electricity from the grid). In other words, if it’s dark and the panels are not generating any electricity, then your car will not charge if solar mode is enabled.

Take off solar mode, and your electric car will charge with a combination of solar electricity (if the sun is out) and grid electricity. Grid electricity can be ‘dirty’, in the sense that some of it may be generated by power stations burning fossil fuels like coal or gas.

The solar mode is a way of ensuring all of your electric driving is 100% emissions free.

The vast majority of solar panels are now manufactured in Asia in state of the art factories.

There are so-called ‘Tier 1’ manufacturers which the influential BloombergNEF has deemed to be ‘bankable’. But being on the Tier 1 list is not a guarantee of quality.

The solar panels available in the UK which are considered to be of high quality include JA Solar, Panasonic, Jinko Solar, Q-Cells, Viridian, Longi, Trina Solar and SolarWatt. This is not an exhaustive list.

Solar panels come with a product warranty like all electronic goods. If a panel fails within the warranty period, it will either be replaced, repaired or you will receive financial compensation. Exactly what recourse you have for a particular solar panel depends on the small print in the warranty document. Product warranties are typically 10, 12, 25 or even 40 years.

In addition, solar panels have a performance warranty. This guarantees how much electricity the panel will produce over time. For example, a panel that outputs 100% of its rated power in Year 1 might only output 80% in Year 25. In this example, there has been solar cell ‘degradation’ of 20% over the 25-year period. Performance warranties usually cover a 25- to 40-year period.

Solar panels produce a type of electricity called ‘direct current’ or DC. However, a home or workplace runs off ‘alternating current’ or AC electricity.

The solar inverter receives the DC electricity and converts it into AC electricity. That AC electricity is then fed into your fuse box where it gets diverted to power whatever devices are switched on.

There aren’t currently any grants when you have a solar panel system installed at home.

You used to be able to get a quarterly payment for solar electricity you generate and export to the grid via the government-backed Feed-in Tariff (FiT) scheme. The scheme closed in 2019.

However, there is a new system called the Smart Export Guarantee scheme, or SEG for short. This began in January 2020 and pays you for any solar electricity you export to the grid, but you have to have a smart meter to be part of the scheme. The money you receive is paid by your electricity supplier who also decides the unit rate you are paid at.

The most common type of solar panel in the UK is ‘photovoltaic’. This simply means the panel produces electricity. You can also see this type of panel referred to as ‘Solar PV’.

There is another type of panel called solar ‘thermal’. These panels don’t generate electricity, but instead they create heat. This heat is then transferred to your home’s plumbing system to provide hot water.

With a clever little device called a ‘solar diverter’ you can even heat your water with solar photovoltaic panels. The diverter monitors how much solar electricity you generate, and – when there is more solar electricity available than the house can use – it turns on the immersion in your water tank. In this way you get free hot water from the sun!

Solar diverters only work if you have an immersion element in your water tank. They don’t work with combi-boilers.

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