Solar generates free electricity during the day; your car charges directly from that generation.
How solar EV charging works
Standard EV chargers draw from the grid. Solar-compatible EV chargers — like the Zappi by myenergi — can detect surplus solar generation and direct it into your car's battery instead of exporting it to the grid.
In practice: on a sunny day with low household demand, the Zappi's Eco mode will start charging your car as soon as panels are generating more than the house is using. On overcast days or at night, it falls back to grid power — ideally on a cheap overnight smart tariff.
The financial case
The numbers become very compelling when you combine all three elements: solar generation, battery storage, and smart tariff overnight charging.
| Charging method | Rate | Cost per 100 miles | Annual fuel cost* |
|---|---|---|---|
| Petrol (average) | ~130p/litre | ~£12–£15 | ~£888–£1,110 |
| Public rapid charger | 55–80p/kWh | ~£17–£23 | ~£1,258–£1,702 |
| Home charger, standard tariff | ~24p/kWh | ~£7 | ~£518 |
| Home + Octopus Intelligent overnight | ~7p/kWh | ~£2 | ~£148 |
| Solar excess (Zappi Eco mode) | ~0p/kWh | ~£0 | ~£0–£50 |
Note
What you need to make it work
- Solar panels: generates the electricity. The larger the system, the more daytime generation available for your car.
- Solar-compatible EV charger (Zappi): detects excess generation and diverts it to the car. Standard EV chargers don't do this — they just draw from the grid.
- Smart tariff (optional but recommended): covers overnight charging when solar isn't generating. Octopus Intelligent is the market leader — it integrates directly with the Zappi.
You don't need a battery to benefit from solar EV charging — the car's own battery is effectively your storage. But adding a home battery means you can store solar generation for both home use and EV charging.
How does it change your solar system size?
If you have or are getting an EV, you should size your solar system larger than you would otherwise.
An EV adds 2,000–4,000 kWh/year of electricity demand (depending on mileage). A standard 8-panel system generating 3,000 kWh/year can barely cover a home's baseline demand, let alone an EV. If you're planning to charge at home, 10–12 panels is a better starting point.
Package 1
Get a quote for solar + EV charging
Solar, battery, Zappi and smart tariff configured as one system.
Combined bill impact: a real example
A customer in Lancashire installed Package 1 (12 panels, 11 kWh battery), a Zappi charger, and switched to Octopus Intelligent for their EV. Their combined electricity and fuel spend before solar: approximately £2,800/year (£1,450 electricity + £1,350 petrol equivalent for a PHEV).
After solar, battery and Octopus Intelligent: approximately £380/year. The system is on track to pay back in just over 5 years.
Frequently asked questions
Do I need a special charger to use solar with my EV?
Yes — a solar-diversion charger like the Zappi detects surplus generation and directs it to your car. A standard EV charger just draws from the grid and doesn't interact with your solar system.
Will solar generate enough to charge my car?
It depends on your system size, mileage and when you charge. A 12-panel system can realistically supply 60–80% of a typical EV's annual charging needs in summer and around 30–40% in winter. The rest comes from overnight smart tariff charging.
What's the best smart tariff for solar + EV?
Octopus Intelligent is widely regarded as the best option for EV owners in the UK. It integrates directly with most major EV brands and with the Zappi charger, automatically scheduling charging to the cheapest available grid slots.
