Let me start by saying I am not an expert but I have SOME experience with (and have working sketches) for:
Arduino + Serial Modbus RTU (Over RS485) + MAX485 Module + PZEM-016 Energy meter (Latest model works with RS485 Modbus RTU).
Arduino + Serial TTL + PZEM-004 + EmonCMS API Posting to EmonCMS.org.
What I would like to accomplish as soon as possible is to combine Nr.1 + EmonCMS API Posting to EmonCMS.org or more preferably API Posting to Local EmonCMS server.
To read the information from a RS485 device was not hard at all and you would just need some information to start with.
I will post the instructions soon as I can see people are eager to read their ebay bought RS485 energy meters and should also work with 3 phase energy meters, inverters, charge controllers, almost anything working on the RS485 Modbus RTU Protocol given you have the required information to start with.