An electric car is the biggest consumer in the house, and the only one that can use up the sun in a few hours. The question on this page: who gets the sun, the home battery or the car? And how do you stop the battery from charging the car with energy you need yourself in the evening?
What evcc is and why the car is not planned by EMHASS is explained in What is evcc?. This page is about the settings.
How the power flows
The EV charger (a Zaptec) sits behind the inverter. The Deye sends solar to the house and the car first, and only then to the battery.
EMHASS deliberately does not know about the car. The car only reduces the grid headroom in the payload: whatever the car draws, the battery cannot charge from the grid. That keeps one owner per actuator: evcc controls the charger, the translator controls the Deye.
The rules in evcc
- The home battery as a meter in evcc, with
prioritySoc60 % andbufferSoc100 %. Below 60 % the battery comes first; above that the car may take the surplus. evcc only reads the battery; it does not control it. - A price limit of €0.25/kWh: below it the car charges fully, above it only on surplus solar.
- Tibber load balancing on the Zaptec, with the 25 A main fuse, as independent protection. It also works when Home Assistant or evcc is down.
Watch the units. evcc reports the charging power in kW, the charger’s integration in W. Convert each source to watts and take the higher of the two. A mistake here left the car in EMHASS’s base load for a few days: EMHASS thought my house used 6 kW at night.
What the translator does while the car charges
- No discharging into the car. If the car draws more than 1500 W, the translator limits the discharge current to what the house needs. The rest of the car’s power comes from the grid.
- Charge current limited to the grid headroom. Grid charging next to a charging car is only allowed up to: grid connection minus car minus the house without the car. Without that limit, 37 A of grid charging next to a charging car was possible, above the 3 × 25 A of the connection.
So the battery supplying about 3 A while the car charges is intended: that is the house, not the car.
What I would do differently
- Test a grid headroom formula straight away with one graph of charge current, SoC and car power side by side. A mistake in that formula cost an afternoon without charging.
- Handle main fuse protection outside Home Assistant from the start, in the charger itself.
- Give every route that can start grid charging (EMHASS, balancing, emergency charging) the same limit, not just the main route.
The incidents behind these lessons are on Lessons from practice (in Dutch for now).
These values apply to one installation. Check them against your own documentation; leave work on 230/400 V to a qualified electrician. Status: October 2026.