Verify units and scaling on one meter, then check that the sub-meters add up to the main incomer within a sensible margin.
Why Sub-Meter
A single incoming meter says how much energy a site uses, not where. Sub-meters attribute energy to tenants, production lines, floors or equipment, which makes waste visible and bills fair.
Meter Types
Clamp-on current meters are quick to fit and suit retrofits. DIN-rail meters are installed in the panel and often measure voltage, current, power and energy together. Three-phase meters report each phase as well as totals. Choose a meter that offers a documented Modbus register map.
Reading the Registers
Energy is usually a counter that only increases, often held in two registers as a 32-bit value, with a scale factor to turn it into kilowatt-hours. Power is an instantaneous value. Some meters use a 32-bit float or a 64-bit integer across four registers instead, and a counter can roll over or reset. Confirm word order, signed or unsigned type and the unit of every register in the manual.
The Balance Check
Add up the sub-meters and compare the total with the main incomer. A difference is expected from unmetered loads and losses, but a large or growing gap points to a missing meter, a wrong scale factor or a wiring problem.
Time Alignment and Solar
Poll related meters together and keep their timestamps so energy lines up across meters. Inverters expose different register sets by model, so give each model its own profile and reconcile generation, consumption and grid import in the same units.
Common Questions
What is energy sub-metering?
Sub-metering measures energy use below the main incoming meter, for example per tenant, floor, production line or machine. It shows where energy goes, supports fair cost allocation and helps find waste. The meters report over a protocol such as Modbus, and a platform collects and compares them.
Why do my sub-meters not add up to the main meter?
Some difference is normal because of unmetered loads and losses. A large or growing gap usually means a missing meter, a wrong scale factor or word order, a different measurement interval, or a wiring problem or a wrong current transformer ratio. Check one meter against a known reading first.