This article is for plant managers, energy managers and production managers who track an overall energy bill and want to link it to what the lines actually produce.
- kWh per good part links the energy bill to what the line produces.
- A stopped machine keeps consuming: heating, hydraulics, auxiliaries.
- A line that loses OEE points sees its EnPI worsen.
- In France, the CEE scheme (fiche IND-UT-134) can fund the measurement, under conditions.
The bill tells you how much the plant consumes. It does not tell you what a part costs, or how much energy goes out while the machines produce nothing. That is the job of a well-chosen energy performance indicator.
Energy efficiency starts with a simple definition
In Energy efficiency: the levers for industry (in French), Acsio Conseil puts it this way: “Energy efficiency means maintaining the same output while consuming less energy.” The article reviews the available levers: energy audits, process modernization, energy management under ISO 50001, heat recovery, insulation, renewable energy. It also lists funding schemes, including French energy savings certificates.
The definition already contains the indicator. If the goal is to produce as much with less energy, you need to track energy relative to output, not energy alone.
kWh per part, the indicator that links energy and production
An energy performance indicator, or EnPI, relates consumption to an activity. In production, the most meaningful one is kWh per good part:
EnPI = energy consumed by the machine (kWh) ÷ number of good parts
The denominator matters. A scrapped part used as much energy as a good one. By dividing by good parts, the EnPI directly captures the quality loss.
Tracked by machine and by day, this indicator reveals what the monthly bill smooths out: a line that is drifting, a product that uses more energy, a crew that leaves equipment idling.
Energy used during downtime, the loss nobody bills for
A stopped machine does not consume zero. Hydraulics, heating, compressors, extraction, workstation lighting: part of the consumption continues whether the machine is producing or not.
| Machine state | What consumes energy | Lever |
|---|---|---|
| Producing | The whole process | Settings, speed, first-pass quality |
| Short stop or micro-stop | Heating, hydraulics, auxiliaries kept running | Reduce stop frequency |
| Changeover | Auxiliaries and sometimes heating | Shorten the changeover, SMED |
| Non-production time (breaks, nights, weekends) | Standby and forgotten auxiliaries | Standby and shutdown procedures |
This is where energy meets OEE. Every unplanned stop consumes without producing. A line that loses OEE points therefore sees its kWh per part rise, even if no equipment has become less efficient.
Reading OEE and EnPI together
| Situation | What it indicates | First action |
|---|---|---|
| OEE steady, EnPI getting worse | A piece of equipment uses more energy for the same work | Maintenance inspection, settings, compressed air leaks |
| OEE falling, EnPI getting worse | Stops consume without producing | Tackle the stops, not the energy |
| OEE falling, EnPI stable | Consumption during downtime is already low | Gains mainly in capacity |
| OEE steady, EnPI stable | Situation under control | Look for consumption outside production hours |
The second row is the most common, and the most counterintuitive: sometimes the best energy lever on a line is a downtime reduction project.
Funding the measurement in France: CEE sheet IND-UT-134
In France, the energy savings certificate scheme (CEE) includes a standardized operation for industry: sheet IND-UT-134, Energy performance indicator measurement system (in French). In the version consulted (A35.2), its conditions include:
- a feasibility study carried out before the work, following steps 1 to 6 of the NF EN 17267 standard;
- data recorded at least every 10 minutes;
- energy management software, since a standard spreadsheet is not enough;
- display of the indicators, comparison with baselines and alarms when a threshold is exceeded;
- installation by a qualified professional.
CEE sheets change regularly and eligibility depends on each project. Specialist public funding firms such as Acsio Conseil check the conditions and put the application together.
Where to start
- Pick the machines that weigh most on the bill: furnaces, presses, compressors, chillers.
- Measure their consumption and their states in parallel for a few weeks: producing, stopped, changeover, non-production time.
- Calculate kWh per good part and the share of energy consumed without producing.
- Start with what requires no investment: standby modes, shutdowns outside production hours, repeated stops.
TEEPTRAK measures energy consumption per machine and machine state on the same time base. kWh per part and energy used during downtime can be read directly, line by line.
Further reading
- Energy efficiency: the levers for industry, Acsio Conseil: all the levers and funding schemes.
- TEEPTRAK: machine and energy monitoring per machine
FAQ
What is an energy performance indicator? It is a ratio that relates energy consumption to an activity, for example kWh per good part. It lets you track energy efficiency independently of production volume.
Why measure energy used during downtime? Because a stopped machine often keeps consuming. That energy produces nothing and raises the cost of every part.
Can EnPI measurement be funded? In France, a dedicated CEE operation exists for EnPI measurement systems in industry, sheet IND-UT-134, subject to conditions. Eligibility is checked project by project.
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