Charging an EV from your own solar is one of the best parts of owning both. But marketing often oversells how much of your charging comes from panels, and the reality is heavily seasonal.
How solar EV charging works
A solar-aware EV charger (Zappi, Hypervolt, Ohme) monitors your home's net export in real time. When you're exporting surplus solar, the charger diverts it into your car instead, ramping up and down to match generation.
Most chargers offer three modes: ECO+ (only charge from solar surplus), ECO (top up from grid if solar is weak), and FAST (full 7kW from any source). ECO+ gives you the cleanest charge but the slowest fill.
The numbers by season
For a typical UK home with a 4kW solar system and an EV doing 8,000 miles/year (~2,000 kWh of charging), here's what to expect:
- April – September: 60–80% of EV charging from solar
- October & March: 30–40%
- November – February: 5–15%
- Annual average: 35–45%
A 6kW or 8kW solar system pushes that annual figure to 50–60%. Adding a 10kWh battery brings it to 60–70%: you store midday excess and discharge it at night while the car charges.
Charger choice matters
Zappi is the established choice: the most mature solar integration and a slick app, but pricey. Hypervolt is the design-led alternative with comparable features. Ohme is cheaper and excels on time-of-use tariffs (cheap overnight grid + solar by day).
The cheap-grid alternative
On a tariff with cheap overnight rates (Octopus Go at 8.5p/kWh, Intelligent Octopus Go at 7p/kWh), charging overnight from the grid can beat solar charging in winter. The numbers are that close. If your export rate is higher than your overnight rate, it can pay to export solar by day and charge the car overnight. A smart charger can pick the split automatically.
