Refueling with the sun: The principle
Filling the battery of your electric car (EV) traditionally costs between 5 and 10 CHF per 100 km when charging at home at the network rate (approx. 25 to 30 cts/kWh in 2026). With solar panels, this cost drops virtually to 0 (or rather to the opportunity cost of the feed-in tariff, often 6 to 10 cents/kWh).
“Smart Charging” allows your terminal to only activate when there is excess solar power on the roof of your house in Switzerland. This is one of the most profitable ways to increase your self-consumption rate.
How does it work technically?
At the center of your electrical installation (in the panel), a smart energy meter (Smart Meter) monitors physical flows. If it detects that your panels produce 6 kW, but your oven and the house only consume 2 kW, that leaves 4 kW free.
Instead of selling these 4 kW for 8 cents to your network manager (Romande Energie, SIG, BKW, etc.), the manager (the inverter or EMS) orders your charging station to activate precisely at 4 kW. The car “drinks” the excess. If a cloud passes and the output drops to 2 kW, the terminal instantly reduces the power sent to the car. The process is 100% automated and prioritizes the home.
Smart charging modes
The majority of modern ecosystems (such as Huawei's FusionSolar or the SolarManager application) offer you 3 modes on your smartphone:
- Pure Solar Mode (Green): The car is not charging THAT when there is solar surplus. If it rains hard, the car does not charge (or remains waiting for a minimum of 1.4 kW surplus, the technical charging threshold for cars).
- Solar + Grid Mode (Mix): Maximum car load (11 kW or 22 kW). The terminal takes all the available sunlight, and “fills” the hole with paid current from the cantonal network.
- Fast Mode (Boost): The network takes over at 100% with maximum speed for an urgent departure.
The Winter Weather Trap
The “wake-up” standard for a typical 1-phase electrical load is approximately 1.4 kW (6 Amps). In winter under heavy fog (typical of the Swiss Plateau), your 10 kW roof may only produce 800 Watts. “Pure Solar Mode” will therefore never be able to start charging. In this case, you must agree to charge at night at the Off-Peak rate, or activate a "Mix" mode which draws the missing 600 W from the network to unblock the process.
Profitability and Sizing
An average electric car consumes 16 to 18 kWh / 100 km. For someone traveling 15'000 km per year (Swiss average), this represents more than 2'500 kWh of annual electricity consumption — that is to say the entire household consumption of an apartment without heating!
It is therefore very often justified in advance to add 5 or 6 additional solar panels to a quote (if there is space left on the roof) if the purchase of an electric vehicle (or two) is planned in the next 3 years. The marginal price of the additional panels (additional kWp) is very low (approx. 500 to 800 CHF per kWp) and they will one day be completely swallowed by the terminal in your garage.