Hi Martijn,
Found the solution, works out-of-the-box, if you have the usb port right 
sensor:
platform: dsmr
port: /dev/ttyUSB0
dsmr_version: 5
group:
meter_readings:
name: Meter readings
entities:
- sensor.power_consumption_low
- sensor.power_consumption_normal
- sensor.power_production_low
- sensor.power_production_normal
- sensor.gas_consumption
Problem Solved