Now that I have my Pi with OpenHabian, I want to buy my first equipment. I’ve been told to start with the RFXCOM as apparently it can read multiple protocols although what I found on the web is that it only does 433MHz. Anyway, as first device I would probably want to start with an energy monitor. Any recommendations?
What you are talking about is a gateway, depending on your energy monitor technology the gateway can be appropriate or no. You have to choose the two components with the same communication techno and protocol.