The Smappee Power Box supports Modbus RTU via its B-Port.
Via this protocol you can read out registers that Voltages, Powers, Currents, calculated and measured via the connected CT Hubs.
Please find the Modbus registers attached:
Smappee Power Box - Modbus registers
Smappee does not provide additional support for custom integrations, reading or writing in the registers of Smappee Power Box is at your own risk