Combining solar panels with an EV charger is one of the smartest energy investments you can make. Here is how to charge your car for free using solar power.
Why Combine Solar and EV Charging?
Electricity from the grid costs around 24p per kWh, while electricity from your own solar panels is effectively free. An average electric car uses around 3-4 miles per kWh, so every free kWh from your solar panels saves you 24p in driving costs. Over a typical 8,000-10,000 miles per year, an EV uses around 2,000-3,000 kWh — costing £480-£720 on grid electricity. With solar panels generating 3,400+ kWh per year, a significant chunk of that driving can be powered by free solar electricity, especially during the sunnier months.
Smart Solar Diversion with myenergi Zappi
The myenergi Zappi is the leading EV charger for solar integration. Its Eco and Eco+ modes automatically divert surplus solar energy to your car instead of exporting it to the grid. In Eco+ mode, the Zappi will only charge using 100% surplus solar power — so your car charges for completely free, albeit at a variable speed depending on how much solar you are generating. In Eco mode, it tops up from the grid to maintain a minimum charge rate while prioritising solar. This smart diversion means you capture solar energy that would otherwise be exported for just 3-15p per kWh.
What Size Solar System Do You Need for EV Charging?
A 7kW home EV charger running on solar needs surplus solar generation to be worthwhile. A 4kW solar system will rarely have a full 7kW surplus (the charger will top up from the grid in Eco mode), but during peak summer months, a 4kW system can generate 3-4kW of surplus if your home load is low during the day. A 6kW or larger system is ideal for EV owners — the extra capacity means more frequent surplus and faster solar-only charging. If you are installing solar specifically to charge an EV, we typically recommend at least a 5-6kW system.
Adding Battery Storage to the Mix
A battery storage system adds another layer of flexibility. Your solar panels can charge the battery during the day, and the battery can top up your car in the evening when you arrive home — even after the sun has gone down. Alternatively, you can charge the battery from cheap overnight electricity (7p/kWh on Octopus Go) and use that stored energy to charge your car during the day. With solar, battery, and a smart charger working together, it is realistic to cover the vast majority of your annual driving miles with cheap or free electricity.
Real-World Charging Costs Compared
Here is how the numbers compare for driving 10,000 miles per year in a typical EV. Charging on a standard electricity tariff (24p/kWh) costs around £600-£720 per year. Charging on an off-peak tariff (7p/kWh) overnight costs around £175-£210 per year. Charging from your own solar panels costs nothing for the electricity itself. In practice, most solar and EV owners use a combination — free solar during the day and cheap off-peak grid electricity overnight — bringing annual charging costs down to well under £200. Compare this to £1,200-£1,800 in petrol for a similar combustion car.
Get Solar and EV Charging Installed Together
At GM Electrical Services, we install both solar PV systems and EV chargers, so we can design a combined system that maximises your solar self-consumption and driving savings. We install myenergi Zappi, SolaX, and Ohme chargers alongside our solar and battery packages. Installing both at the same time often saves money on installation costs and ensures everything is configured to work together optimally from day one.
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