Using solar power to charge an electric vehicle can reduce how much electricity you need to buy from the grid. But one question often comes first: how many solar panels would you actually need?
There is no single number that works for every home. For anyone considering solar panel installation in Leicester, the answer depends on annual mileage, EV efficiency, panel output, roof conditions and how much of the generated electricity is also used elsewhere in the house.
A useful starting point is to calculate how much electricity your EV needs over a year.
Start With Your Annual EV Energy Use
EV efficiency is usually measured in miles per kilowatt-hour, or miles/kWh.
The RAC currently uses an assumed efficiency of around 3.5 miles per kWh when comparing EV charging costs, although real-world efficiency changes with vehicle type, driving style, temperature and road conditions.
For example, if you drive 8,000 miles each year:
8,000 ÷ 3.5 = around 2,286kWh
So, roughly speaking, your EV might need around 2,300kWh of electricity annually.
That does not mean your solar panels need to generate exactly 2,300kWh solely for the car. Your household appliances are also competing for the electricity produced by the panels.
How Much Electricity Can One Solar Panel Generate?
Solar panels are normally discussed in terms of their peak output, measured in watts or kilowatts peak.
A modern domestic panel might commonly be around 400W to 450W, although exact specifications vary between products.
Energy Saving Trust says the average UK domestic solar system is around 4.5kWp and approximately 12 panels, covering roughly 20–30m² of roof area.
UK solar generation also varies by location and installation conditions. Established UK calculation guidance indicates that 1kWp of installed solar capacity can typically generate roughly 720–940kWh annually under favourable orientation and limited shading.
So the number of panels needed cannot be calculated from wattage alone.
A Practical Example
Suppose your EV needs around 2,300kWh annually and your chosen panels are rated at 450W each.
Six panels would create an array of:
6 × 450W = 2.7kWp
Seven panels would provide 3.15kWp, while eight would provide 3.6kWp.
Depending on roof orientation, shading and local conditions, a system in this range could potentially generate an annual amount of electricity broadly comparable with the energy needed for moderate EV mileage.
However, that does not mean six, seven or eight panels will charge your EV entirely from solar throughout the year.
This distinction is important.
Annual Generation and Direct EV Charging Are Different
Solar generation is highest during daylight hours and generally stronger during spring and summer.
Your EV may be parked away from home during those hours.
You may therefore generate surplus electricity while the vehicle is elsewhere, then charge the car from the grid later in the evening.
Energy Saving Trust gives a real-world example of a household whose solar system generated approximately as much electricity annually as the home and EV consumed combined. However, only around 40% of the generated electricity was actually used directly in the property, with the rest exported.
That is why panel numbers should not be based solely on annual EV mileage.
For a broader introduction to PV generation, see Everything You Should Know About Solar Panels.
What Factors Change the Number of Panels You Need?
A properly designed system should consider several things together.
Your mileage
Someone driving 4,000 miles per year will require much less charging energy than someone covering 15,000 miles.
Your EV’s efficiency
Smaller efficient EVs generally use less electricity per mile than larger or heavier vehicles.
Roof direction
A south-facing unshaded roof generally provides the strongest annual performance.
East- or west-facing roofs can still work well, but Energy Saving Trust notes they may generate around 15–20% less energy than an equivalent south-facing system.
Shading
Trees, chimneys and nearby buildings can reduce panel output.
Household electricity use
Solar generation will normally supply your home first, so appliances, heating equipment and other electrical loads affect how much surplus electricity remains for the EV.
This is why solar energy in Leicester should be planned around total household demand rather than just the car.
Do You Need a Solar-Compatible EV Charger?
If your aim is to charge using surplus solar generation, charger choice matters.
Some smart chargers can monitor excess solar electricity and adjust EV charging accordingly.
Without suitable integration, you may still use solar-generated electricity indirectly, but you will have less control over whether charging follows available surplus generation.
Anyone arranging EV charger installation in Leicester should therefore mention solar PV plans at the design stage.
You can also read Should You Install Solar Panels Before Getting a Home EV Charger? for more guidance on planning both systems together.
Would a Battery Help?
Battery storage can increase how much of your own solar electricity you use, but it does not automatically mean more panels are required.
A battery can store some surplus daytime generation for use later.
However, EV batteries are much larger than typical home batteries. It may therefore be more efficient in some households to charge the vehicle directly when solar generation is available rather than repeatedly moving electricity through another battery.
Your driving routine, tariff and household consumption should all be considered before deciding.
Are There Any Installation Rules to Consider?
Solar PV systems connected to a home must be registered with the Distribution Network Operator. Your installer will normally handle the relevant notification or application.
Domestic rooftop solar in England is often permitted development, although conditions and exceptions apply, particularly for listed buildings, conservation areas and certain installations.
An EV charger installation in Leicester also needs to be assessed as part of the home’s electrical system, especially where both technologies are being installed together.
Experienced EV charger installers in Leicester should consider the supply capacity, charger load and solar equipment rather than treating each system separately.
So, How Many Panels Should You Plan For?
For moderate EV mileage, a system of roughly six to eight modern 450W panels may generate an annual amount of electricity comparable with the EV’s yearly charging demand in suitable conditions.
But that should only be treated as an illustration.
Your actual requirement may be higher or lower depending on mileage, panel output, roof direction, shading, household consumption and when the vehicle is available to charge.
The best approach is to size the solar array for the home as a whole, then design the EV charging strategy around the electricity the system is expected to generate.
Planning Solar and EV Charging Together?
East Goscote Electrics Limited can assess your electricity use, roof suitability and EV charging needs to help determine an appropriate solar PV and charging setup.
Contact East Goscote Electrics Limited to discuss your requirements and explore how home solar generation and EV charging could work together.
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