Electric vehicles and home batteries are increasingly being purchased together — and for good reason. A home battery can smooth out the EV charging load and maximise the proportion of your driving powered by solar. But the two systems also interact in ways that affect sizing and economics.
Can a home battery charge an EV?
Yes, but with caveats. A home battery typically stores 5–15 kWh and can discharge at 5–10 kW. A standard EV charger (7.2 kW) draws around 7 kW. So in theory, a battery can power an EV charger at full speed for 1–2 hours before being depleted.
In practice, you'd want a much larger battery if you're planning to charge a full EV overnight from battery alone. A typical EV uses 15–20 kWh per 100 km; daily commuters who drive 40 km need roughly 6–8 kWh per night.
Solar charging for your EV
The more financially compelling use case is solar-direct EV charging: using surplus solar generated during the day to charge your EV. If you're home during the day or can schedule EV charging for midday, you can often charge from solar without a battery at all.
Where a battery helps: if you're not home during the day, a battery can accumulate the daytime solar surplus and then dispatch it for EV charging in the evening when you plug in.
How much does EV charging add to your battery size?
Each kilometre of EV travel you want to power from solar adds roughly 0.15–0.20 kWh to your battery requirement (accounting for round-trip battery efficiency of ~90% and EV charging efficiency of ~90%).
For 40 km/day of solar-powered commuting, add approximately 7–8 kWh to your battery sizing estimate. Our calculator includes an EV load toggle that adjusts the recommendation automatically.
Bidirectional charging (V2H / V2G)
Some EV models (including some Nissan LEAF, Hyundai Ioniq 5/6, and upcoming models from other manufacturers) support vehicle-to-home (V2H) or vehicle-to-grid (V2G) charging, where the EV battery can power your home.
This is an exciting development that could make a dedicated home battery redundant for some households — but V2H/V2G is still limited in Australia by charger availability, grid regulations, and vehicle compatibility.
The combined system: solar + battery + EV
A well-sized combined system:
- 6–10 kW solar system
- 10–15 kWh home battery
- 7.2 kW Level 2 EV charger
...can cover the majority of a household's electricity consumption and most EV charging needs from solar. The economics improve significantly as the EV displaces petrol costs that would otherwise go to a petrol or diesel vehicle.
Tips for EV + battery owners
- Schedule EV charging for after sunset so it draws from the battery rather than competing with appliances for solar during the evening peak
- Use smart charging (OCPP-compatible chargers) to integrate with your home energy management system
- Oversize your solar if possible — more generation means more surplus to fill both the battery and the EV