KNX with solar, batteries, and EV charging: building the energy hub

A modern residential project often includes solar panels, a home battery, and an EV charger. The customer expects them to work together: charge the car from solar surplus, run the house from the battery overnight, sell back to the grid when battery is full. KNX is the orchestration layer.

The inverter is usually the constraint. Most solar inverters speak Modbus TCP or RTU rather than KNX directly. A Modbus-KNX gateway translates inverter data points (PV power, battery state of charge, grid import/export) into KNX group addresses. From there, the KNX system can react.

EV chargers expose status through OCPP (the Open Charge Point Protocol) or a vendor-proprietary REST API. Some support Modbus too. The choice of charger has a bigger impact on integration smoothness than the brand of the rest of the system; pick a charger that publishes power, state of charge, and a setpoint for charging current. The setpoint is what lets KNX dynamically dial the charging rate up and down to match solar surplus.

The orchestration logic. A simple but effective rule: if solar surplus exceeds 1 kW, increase EV charging current. If household load rises (washing machine, oven, AC), decrease EV charging current. If battery is below 20 percent and solar is gone, charge the battery before the car. These rules sit in a logic block in the visualization server or directly in a KNX logic gateway.

Documentation matters. The customer wants to see where their energy went today. A visualization with three charts (solar generation, household consumption, battery state of charge) and a daily summary email keeps them engaged. Engagement is what makes them invest in further measures.

Finally, plan the EEBus future. EEBus is an emerging European standard for energy device interoperability. Some manufacturers are already shipping EEBus-capable inverters and chargers. Bridging EEBus to KNX through a gateway is straightforward and future-proofs the home for grid services.