How to calculate heating energy consumption with central heating system

Hi everyone.
Here is my challenge.
I have installed an homematic IP thermostat in all my radiators. I live in a condo with central heating system.
The homematic IP thermostat is making available to HA the % of valve opening.

I would like to do the following:
1- Calculate the instant consumption in W based on the valve opening
2- Use the integral sensor to calculate the energy in kWh
3- Use the meter sensor or grafana to calculate the consumption per period of time

2 and 3 are not an issue.
I am struggling to find a decently accurate way to derive the instant power from the valve opening.
It does not have to be super precise, I am more interested in comparing consumption over time.

Can anyone help me? Has anyone done something similar?


Have you figured it out? I am just thinking about how to calculate it properly. My first move will be to calculate in artificial units to compare months only, but Watts would be nice.