How do charging and solar power work together?
A second case, in another season: a sunny Saturday in June. The panels on one roof in the street deliver 4.5 kW; the house uses less than one.
The car stands in the driveway at 40%.
The questionCan the car charge with what the roof produces, and what decides how much?
A composed day with a roof of about 6 kWp. Between roughly 9 AM and 5 PM, the surplus exceeds the minimum a car can charge with on one phase (6 A × 230 V ≈ 1.4 kW).
The minimum matters
A car cannot charge at any power: the control signal of the cable cannot ask for less than 6 A, so that is the least a car can draw. On one phase that is about 1.4 kW, on three phases about 4.1 kW. A wallbox that switches between one and three phases can follow a small surplus in the morning and a large one at noon.
- : the car takes only what the roof delivers beyond the house.
- Minimum plus surplus: the car charges at least the minimum from the grid and adds the surplus.
Why the car fits
A car battery holds far more than a household uses in a day, and this car stands at home at weekends and in the evening. Charging at midday also matches the hours when solar generation peaks and prices can fall, see stop 05. On workdays, workplace charging can play the same role for solar on office roofs.
Check your understanding
3 questions. Answer all of them to complete this stop. Each answer explains itself.
About what minimum power does a car need to charge on one phase?
The cable's control signal cannot ask for less than 6 A; on one phase at 230 V that is about 1.4 kW.
Why does phase switching help with solar charging?
The minimum on three phases is about 4.1 kW; on one phase, charging can start from about 1.4 kW.
Why is a car a good consumer for rooftop solar?
A large battery and long standing times let charging follow the sun.
- Surplus charging Charging only with the solar power a household does not use itself, above the car's minimum charging power. Glossary
- Beckhoff Automation: EL6761 documentation, IEC 61851 low-level communication: table of duty cycles and the maximum current each allows (6 A at the lowest). https://infosys.beckhoff.com/content/1031/el6761/18724365579.html. Checked 13 Oct 2026.
- Bundesnetzagentur, SMARD: The challenge of solar peaks: solar generation peaks at midday, and prices fall to zero or below when more electricity is available than needed. https://www.smard.de/page/en/topic-article/5892/217174/the-challenge-of-solar-peaks. Checked 13 Oct 2026.