Calculate how many free solar miles you can drive each year and your annual saving on EV charging.
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Solar panels generate the most power between 9am and 4pm on sunny days — which overlaps with typical work-from-home hours or days when the car is parked at home. The more you can align charging with generation, the more free miles you get.
A standard 7 kW home charger charges whenever you plug in. If you plug in overnight, essentially none of it is solar. If you plug in after a sunny day, you may capture some. Average capture: ~15–25% of solar generation.
EV chargers like Zappi, Ohme, or Wallbox Pulsar can detect surplus solar and divert it to the car automatically. They start charging when generation exceeds household demand, then ramp up and down in real time.
If your car's app supports charge scheduling, set it to charge midday (e.g. 10am–3pm). This works if you leave the car plugged in during the day. Not as reactive as a smart charger but costs nothing extra.
A smart solar charger costs £500–£900 installed vs. ~£500–£700 for a standard unit. If you're already getting solar, the upgrade cost is often £200–£300. With a 4 kWp system and 10,000 miles of annual driving, the extra solar capture vs. a standard charger is worth roughly £50–£120/yr — payback on the charger upgrade in 2–6 years on top of the standard charger's payback.
If you have both solar and an EV, a time-of-use tariff can significantly improve your economics. The goal: export at a high rate during the day, import cheaply at night for EV charging.
Intelligent Octopus Go
6-hour overnight cheap rate (~7–9p/kWh) for EV charging. Standard rate for household use. Works with smart charger integration — the car charges itself at the cheapest time.
Octopus Flux
Three time-of-use bands: cheap overnight, standard midday, peak in evening. Pairs well with a battery — charge the battery cheaply at night, export during midday peak, avoid peak pricing.
Agile Octopus
Prices vary half-hourly tracking wholesale rates. Can give very cheap (or even negative-price) rates overnight. Requires more active management but can save significantly with automation.
Even without solar, an EV is cheaper per mile than petrol at current UK energy prices. Solar charging reduces that gap further — substantially if you have a smart charger and drive a lot.
| Scenario | Cost/mile | 10k miles |
|---|---|---|
| EV + solar (smart charger) | ~5–8p | ~£500–800 |
| EV — overnight standard rate | ~8p | ~£800 |
| EV — Intelligent Octopus Go | ~2–3p | ~£200–300 |
| Petrol (40 mpg, 140p/L) | ~17p | ~£1,700 |
| Diesel (50 mpg, 150p/L) | ~14p | ~£1,400 |
August 2026 prices. EV efficiency: 3.2 mi/kWh average. Public charging excluded (typically 60–90p/kWh).
Read our full guides on costs, battery storage, and the Smart Export Guarantee before you get quotes.