Solar Panels and Electric Vehicles
Combining rooftop solar with an electric vehicle is one of the most powerful money-saving combinations available to homeowners today.
The Economics
An average EV driven 15,000 km/year consumes about 2,500–3,000 kWh of electricity.
Charging from the grid: At €0.20/kWh, that's €500–€600/year in fuel costs (already much less than petrol).
Charging from your solar panels: Nearly €0 in fuel costs. The marginal cost of solar electricity you've already paid for is effectively zero.
Over 10 years, solar + EV saves €5,000–€6,000 compared to grid charging — and €15,000–€25,000 compared to a petrol car.
How Much Extra Solar Do You Need?
To cover your EV charging from solar, add 1.5–2 kWp to your system size:
| Annual Driving | Extra kWh Needed | Extra Panels |
|---|---|---|
| 10,000 km | ~1,800 kWh | 4–5 panels (1.5 kWp) |
| 15,000 km | ~2,700 kWh | 6–7 panels (2.5 kWp) |
| 20,000 km | ~3,600 kWh | 8–9 panels (3.0 kWp) |
Timing Your Charging
The key challenge: most people drive during the day when solar produces the most. Solutions:
Home charging at night + battery — a home battery stores daytime solar for overnight EV charging. Effective but expensive.
Daytime charging when home — if you work from home or have a second car that stays home, charge during peak solar hours.
Smart chargers — EV chargers like Zappi, go-e, or Easee can be set to charge only when solar surplus is available. The car charges variably throughout the day as production allows.
Weekend charging — charge fully on weekend days when you're home and production is high.
The Right Charger
A dedicated home EV charger (wallbox) is strongly recommended over a standard outlet:
- Standard outlet: 2.3 kW — charges ~10 km/hour. Safe only with proper wiring.
- Wallbox (7.4 kW single phase): ~35 km/hour. The sweet spot for home charging.
- Wallbox (11 kW three phase): ~55 km/hour. Future-proof, but requires three-phase power.
Cost: €500–€1,500 installed.
System Sizing for Solar + EV
When using our calculator, add your expected EV consumption to your household consumption to get the right system size. A household that uses 5,000 kWh/year plus an EV needing 2,500 kWh/year should size for 7,500 kWh/year of production.