Solar Surplus Charging

Use excess solar energy to charge the electric car. This is the core function of evcc.

Solar mode

The function can be activated at the charging point via Solar mode.

In this mode, charging starts automatically as soon as the PV system delivers enough power. The charging power is continuously adjusted so that no power is drawn from the grid if possible. If the PV system no longer delivers enough power or if household consumption increases, charging is paused and continued later.

When does charging start?

All electric cars have a minimum charging power. This is determined by the minimum current of 6 A specified in the charging standard IEC 61851. The minimum charging power depends on the number of phases that the car and wallbox use for charging.

Phases	Minimum charging power (6 A)	Maximum charging power (16 A / 32 A)
1-phase	1,4 kW (1 x 6 A x 230 V)	3,7 kW (1 x 16 A x 230 V)
2-phase	2,8 kW (2 x 6 A x 230 V)	7,4 kW (2 x 16 A x 230 V)
3-phase	4,1 kW (3 x 6 A x 230 V)	11 kW (3 x 16 A x 230 V) 22 kW (3 x 32 A x 230 V)

Most wallboxes today are connected three-phase (11 kW or 22 kW). This means that the minimum charging power is 4.1 kW. For wallboxes with automatic phase switching (1P/3P), evcc can switch between single-phase and three-phase as required and start charging at just 1.4 kW.

The feed-in power is shown in the energy flow diagram. If the surplus is above the minimum charging power for a certain period of time, charging starts.

Energy flow diagram shows 3.4 kW feed-in.

Note: The value on the grid meter is the decisive factor. Solar mode does not work for systems with regulated grid feed-in (“zero feed-in”).

Not enough surplus?

By default, the system tries to avoid drawing any power from the grid. You can adjust this behaviour under Configuration → Charging points & Heaters → [My Charging Point]. In the Behaviour section, switch the Solar setting from maximum solar to custom. You can then set your own thresholds and delays.

Enable grid power defines how much surplus must be available before charging starts. The value is negative because it refers to power exported to the grid, e.g. -2,000 W means 2,000 W of surplus. With the default value of 0 W, charging starts as soon as the minimum charging power is available as surplus. The Enable delay defines how long this surplus must be available continuously before charging starts, e.g. 1 minute.

Disable grid power defines how much power may be drawn from the grid while charging before it stops. With 2,000 W, for example, charging continues as long as no more than 2,000 W is imported from the grid. With the default value of 0 W, charging stops as soon as the minimum charging power is no longer covered by surplus. The Disable delay defines how long this limit must be exceeded before charging stops, e.g. 30 minutes.

This can be particularly useful for small solar systems or in the winter months, in order to at least partially cover your own charging needs with solar energy.

The thresholds and delays should be selected so that charging is not switched on and off too often. Some vehicles refuse to charge if it is interrupted too often and must be made to charge again, for example by unlocking or plugging/unplugging the charging cable.

Interaction with the home battery

Battery systems have their own, fast regulation. In the standard case, the home battery has priority. The Solar mode only starts charging the vehicle when it can no longer absorb any power.

You can find out how to adjust this behavior under Home battery.

Min+Solar mode

The Min+Solar mode is a variation of the Solar mode.

Here, charging begins immediately with minimal charging power - even if there is no or insufficient surplus. If surplus is available, the charging power is increased accordingly.

In contrast to Solar mode, charging is not interrupted. This is primarily useful for vehicles that do not like regular starting and stopping of charging.

Even in very changeable weather conditions, Min+Solar mode can be a good alternative to Solar mode.