Modern energy meters (Schneider iEM, Socomec Diris, Janitza UMG, Siemens SENTRON) typically expose their measurements (kWh, kVARh, U, I, P, cos phi) over Modbus RTU or TCP, mapped onto standardised or vendor-specific registers.

Energy meters are the number-one Modbus use case in modern tertiary BMS. Typical mappings include: Schneider iEM with a documented register list and around 50 measurements; Socomec Diris A40 with about 80 measurements including harmonic THD; Janitza UMG, which is very comprehensive and supports multi-circuit installations; and Siemens SENTRON PAC, integrated with TIA Portal. Good practice is to test the register map with mbpoll before binding it into the BMS, because vendor documentation is sometimes imprecise.

Read at least two energy meters in parallel against a known clamp meter the first time you commission a building: a half-percent discrepancy is normal, a factor of two means a wrong byte order or CT ratio.