A house and a port

We recently bought this house. It's a great place and everything is brand new.
So what do you do when you own so many (tech) goodies? Indeed, I googled all manufacturers and model types of devices that are scattered throughout the house, just to learn more about their possibilities:

• Kamstrup 162J electricity meter
• Flonidan Uniflo G4S gas meter 
• Elster V200 water meter
• Ferroli AquaSol 4 LB-90-IT solar water heater
• Intergas Kombi Kompakt HRE 28/24 central heating unit

On Tweakers forum I found some interesting articles about these 'smart meters'. Especially the mention of a so-called P1 communication port triggered my curiosity, but I was convinced my meter did not have such a port... "I surely would have seen that immediately".

Just to be certain I checked the meter.... and I saw it right away, covered with a black soft plastic cover, there was an RJ11 socket, begging to be used.

So I was left with these questions: what data can we read from this P1 port? And what can we do with the data? A new project was born.