The indicators: kWh per piece and idle consumption
Total consumption says how much you spend; energy per piece says whether you spend it well, because it takes account of how much was produced. Idle consumption, with the machine stopped, shows the waste that does not depend on production.
Energy in the period = meter reading at the end − reading at the start
kWh per piece = energy in the period ÷ good pieces in the period
Idle consumption = energy drawn while the line is not producing
Peak power = maximum active power in the period
The guide to energy consumption monitoring explains which KPIs to choose and where to start.
What the dashboard shows
- kWh per line and per shift, comparing shifts and weeks.
- kWh per piece by order and item, from the pieces counted by the PLC and the orders in the ERP.
- Idle consumption: how much the lines draw at night, at weekends and during stops.
- Power over time and its peaks, to see which start-ups overlap.
- Unusual consumption: draws out of the ordinary for that hour and day, flagged by an alarm.
The registers to read
| Quantity | Where it usually sits | What it is for |
|---|---|---|
| Imported active energy | A 32- or 64-bit register of the meter | Consumption in the period, by difference |
| Active power | A register of the power analyser | Load curves and peaks |
| Power factor, voltages, currents | Registers of the power analyser | Diagnosis and power quality |
| Pieces produced | The part counter of the line PLC, for example Siemens S7 | Energy per piece |
The register map is in each instrument's manual. Orders and items come from the ERP, the shift calendar from an Excel file.
The steps in Muvia Industrial
An edge node is installed on the switchboards' network and enrolled with a token.
On the node you add the Modbus TCP driver for each meter or analyser: address, unit id and the registers to read, each with a name. If there is a Siemens S7 PLC on the same line, the same node reads its part counter.
With Edge Functions the data can be converted on the node already, for example from Wh to kWh or by applying the current transformer ratio.
The ready-made “Consumption over a period” analysis turns the cumulative counter into kWh per hour, per shift or per day, line by line; a Python function, run every night by a flow, joins them with pieces, orders and shifts and writes the kWh per piece.
The dashboard shows lines, shifts and pieces; an alarm opens on unusual consumption, and every month a PDF report goes out by email.
The pitfalls of Modbus registers
- Word order: a 32-bit value takes two registers, and some instruments put the high word first, others the low one. With the wrong order the numbers look random.
- Scale and unit: a register may be in Wh, in kWh or in hundredths of a kWh, and some instruments must be multiplied by the current transformer ratio. A comparison with the first month's bill avoids errors by a factor of ten.
- Counters that reset: after a replacement, or on reaching their maximum, counters restart; energy must be calculated on increments, recognising the jump.
- Energy from power: adding up power readings taken at irregular intervals gives an approximate energy. When there is an energy counter, use that.
- Shared loads: compressors, lighting and air conditioning serve several lines; allocate them with a declared rule, or show them apart.
Frequently asked questions
No: the driver reads Modbus TCP. Serial-only instruments are usually connected through a serial-to-TCP converter.
For energy per shift and per piece, one reading a minute of the energy counter is enough; to see the power peaks of start-ups you need more frequent readings from the analyser. Frequency is chosen per driver.
Yes: kWh per line and per shift, idle consumption and peaks are useful on their own. Pieces are needed only for energy per piece.
The node keeps reading and holds the data in a local buffer until the connection returns. The energy counter does not lose count anyway: the difference between two readings stays right.