For users wanting to use their own software for reading the meters, Modbus is their most likely choice. This protocol has been around since the 1980s and is one of the most common protocols for industrial controls. It requires a separate Modbus address be assigned to each meter, and the meter data is retrieved from numbered registers. When ordering a meter, choose this option only if you have Modbus compliant software. EZMeters support Modbus RTU.
Davidge is happy to provide a free utility program for setting up a Modbus system. It is available for Windows, OS-X and Linux. Setup instructions and port addressing is in the Modbus Installation Guide