How does solar-surplus charging work?
An energy meter in your fuse box sees how much power your panels generate and how much your home uses. Whatever is left goes to your car. If the sun weakens or the washing machine starts, the charging station charges more slowly or pauses briefly.
Not every charging station can do this. With us, the Zaptec Go 2 can, via the Zaptec app. It's a different function from load balancing: load balancing protects your supply, solar-surplus charging sends your own power to your car.
A car needs a minimum
A car charges at a minimum of 6A. On a single phase that's about 1.4 kW, on three phases about 4.1 kW. If the surplus is smaller, the car doesn't charge or tops up from the grid. On cloudy days or in winter you'll therefore get less out of solar than in summer.
When does it work well?
- Your car is at home during the day, for example when you work from home, or at weekends.
- You have enough panels to power your car as well as your home.
- You don't need a full car every day: solar charging is slow and variable. For a quick top-up, simply use grid power.
If you're often away during the day, you'll charge less on solar. Charging at home overnight then remains the basis.
And a home battery?
A home battery is often 5 to 15 kWh, a car battery often 40 to 80 kWh. If you charge your car from your home battery, it empties quickly and can't power your home in the evening. A home battery also often only supplies a few kW at a time.
That's why this usually works best: during the day you charge your car directly with solar power, and your home battery saves the rest for your home in the evening. If your system can exclude the car from the home battery, turn that on. How that works for your battery is in its manual or app.
With a portable charger
A portable charger doesn't automatically follow your panels. You can, however, set it to a low setting during the day, for example 6A (about 1.4 kW), so your car mainly charges with what your panels generate. Also read Portable charger or charging station: which suits you?