Charging with PV solar power: wallbox, storage & tariffs

How the interplay works

1. The PV plant generates electricity.
2. The electricity first supplies the refrigerator, heat pump and other household appliances.
3. An energy meter checks whether there is any solar power left afterwards.
4. With enough surplus, the wallbox starts automatically.
5. If the solar power is no longer sufficient, the charging can pause or use grid electricity, or the battery storage as well.

What you normally need for this

• PV plant with inverter
• Wallbox with PV surplus charging
• Energy meter or energy management system
• Elektroauto
• Optional: Home storage and dynamic electricity tariff

Wallbox and PV surplus

An electric vehicle cannot charge with arbitrarily low power. For true surplus charging, approximately 1.4 kW single-phase or 4.2 kW three-phase is required. With changing cloud cover, the wallbox should therefore be able to fine-tune the charging power.

Es gibt zwei typische Operating modeen:

Beispiel: The PV plant generates 6 kW while the house needs 2 kW. The wallbox can charge approximately 4 kW into the car. If household consumption rises or solar output drops, it reduces the charging power or pauses.

What does the battery storage bring?

A battery storage is not strictly necessary. It stores surplus solar power during the day and makes it available for the car in the evening or at night. This is especially helpful if you are not at home during the day.

The sensible priority depends on your settings:

1. Household first.
2. Danach eventuell Hausspeicher.
3. Dann Elektroauto.
4. Surplus that is not needed is fed into the grid.

If the car must be urgently charged in the evening, the energy management can deliberately make the storage available for the vehicle. However, this creates additional conversion losses.

Which tariffs fit?

Normaler Haushaltsstrom

The car charges with your existing electricity tariff when the PV output is insufficient. This is simple, but less economical when grid electricity is expensive.

Dynamic electricity tariff

The electricity price is at times aligned with the market price. A compatible wallbox can then preferentially charge the car at night or during cheap hours when no solar power is available. Dynamic tariffs therefore complement PV surplus charging mainly in winter and at night.

Please note:

• The market price is not automatically the final price.
• Grid fees, taxes, levies and charges are added on top.
• You usually need an intelligent metering system or a suitable meter.
• For automatic charging, the car, the wallbox and the tariff must technically work together.

Separater Autostromtarif

With a separate meter, the car can use a cheaper charging tariff. In combination with PV, a specific metering concept is often needed so that first your own solar power and then vehicle electricity as needed can be used.

What is usually the best solution?

For many households, this combination makes sense:

• PV plant with sufficient output.
• Wallbox with continuously adjustable PV surplus charging.
• Energy meter at the grid connection point.
• Charging during the day, when the car is at home.
• Dynamic tariff as a supplement for night and winter charging.
• Battery storage only if the additional self-consumption and the evening charging justify the price.

How cheap does solar power become for charging?

• PV self-consumption + wallbox: €0.10–0.30/kWh — depending on the size of your system and the level of investment.
• Utilization rate with storage: Up to 80 % of the PV power is used directly in the house — even at night.
• Capacity vs. effort: Bigger panels → higher investment, but low electricity costs per kWh.