This article is for plant managers, production managers, energy and maintenance leads and continuous improvement teams who have a list of possible energy saving measures in front of them and need to decide where to start. It explains why the number of hours a machine spends switched on but not producing often changes the ranking of measures more than its rated power does, and how to combine measured machine states with measured consumption to set the order.
- Without measurement, there is no reliable order of measures.
- Energy without production is power in a state times hours in that state.
- Ranking by rated power often points to the wrong machine.
- Measures without investment usually target the hours without production.
What dswerk.de writes about measurement and the order of levers
In the German article Energieeffizienz im Maschinenbau: Hebel & Wirtschaftlichkeit (Energy efficiency in mechanical engineering: levers and profitability), Dipl.-Ing. Dražen Stjepić describes on dswerk.de how manufacturing companies in mechanical engineering can cut their energy use and work out the business case for investments. Right in the introduction, one sentence sums up the logic of this article: “Ohne Messung gibt es keine Kennzahlen, ohne Kennzahlen gibt es keine Priorisierung” (“without measurement there are no indicators, without indicators there is no prioritization”).
He recommends measuring the largest consumers separately first, for example with sub-meters, and presents five levers: more efficient electric motors, variable frequency drives on pumps and fans, compressed air (leaks, pressure, control), demand-driven hydraulics and avoiding load peaks. To get started, he suggests a clear order: compressed air leak detection, then sub-meters, then variable frequency drives on existing pumps and fans, with larger system projects only after that. A practical example from his article shows what is at stake here: two CNC machines that kept running in weekend standby with full hydraulic pump power. And for specific energy consumption per part, he advises recording changeover, downtime and cleaning times over the same period. This article picks up exactly that point: how the measured states of each machine help you prioritize the measures.
Why the hours without production change the ranking
The energy a machine uses without making a single part is the product of two values: the power it draws in that state and the time it spends in that state. Sub-meters give you the first value. The second is missing in many plants, because nobody knows exactly how long a machine waits, changes over or stays powered after the end of the shift each week. If you rank only by rated power, you often start with the wrong machine.
For prioritization, it helps to split each machine’s time into clearly separate states:
- Production: the machine is making parts. This is where levers such as more efficient drives or variable frequency drives apply.
- Micro-stops: stops lasting from a few seconds to a few minutes. Hydraulics, cooling and extraction usually keep running.
- Waiting during the shift: missing material, no operator, pending release. The machine is ready but not producing.
- Changeover and cleaning: planned time without production, during which all utilities often stay on.
- Planned downtime: breaks, nights and weekends without a shift. The question here is whether the machine is really switched off or stays in standby.
Measures aimed at the states without production (shutdown logic, energy saving mode, shutting off compressed air, demand-driven hydraulics) pay off in proportion to the hours spent in those states. A mid-sized machine that waits for many hours or stays in standby at the weekend can therefore rank ahead of a larger machine that is producing almost all the time.
The prioritization matrix: state, measurement, lever
| State | What the measurement shows | Typical lever | Type of measure |
|---|---|---|---|
| Planned downtime (nights, weekends) | Hours powered without a shift, standby power | Shutdown routine, standby program in the controller, isolating utilities | Organization or programming, usually without major investment |
| Waiting during the shift | Duration and frequency of waiting time, with cause | Energy saving mode after a set waiting time, removing the causes of waiting | Process and control |
| Micro-stops | Number and total duration per shift | Eliminating the causes of micro-stops | Improvement work, also raises OEE |
| Changeover and cleaning | Actual duration per event | Switching off utilities selectively, shortening changeovers | Standard work |
| Production | Productive hours and consumption per part | More efficient motors, variable frequency drives, load sensing hydraulics | Investment with a payback calculation |
The matrix does not replace a business case. It makes sure the business case is built on the right number of hours, and that measures without investment, which often target the hours without production, are not overlooked.
A five step method
- Select the machines. Start with the largest consumers, as dswerk.de recommends for sub-meters, and add the machines you know often wait.
- Measure states, including outside shifts. Record automatically over several weeks when each machine is producing, stopped, waiting or changing over, including nights and weekends.
- Determine power per state. Put the meter readings next to the state history and work out the average power of each machine in each state.
- Calculate energy without production and rank. Hours per state times power per state gives the energy used without production. Rank the machines by that figure, not by rated power.
- Assign levers and measure again. Assign a lever from the matrix to each large item, start with the measures that need no investment, and measure again after implementation.
An illustrative example, not measured data: machine A draws 5 kW when not producing and stays powered for 60 hours a week without producing. That is 300 kWh a week. Machine B is larger and draws 8 kW when not producing, but only stands idle for 15 hours a week. That is 120 kWh. By rated power, B would come first; by energy without production, A is the first candidate, and the right lever is a shutdown routine, not an investment.
Two mistakes are common. First, waiting time during the shift is counted as production time because the machine is switched on. Second, nobody measures again after a measure, so the saving remains an estimate. Measuring machine states answers both questions with data.
What TEEPTRAK contributes
TEEPTRAK measures the state of each machine automatically: a module in the electrical cabinet and a sensor on the line, about one hour of installation per machine, no connection to the PLC, first OEE within 48 hours. Every stop is recorded with a timestamp, including micro-stops, and operators confirm the cause at the machine, so waiting for material or for release shows up as its own cause. Consumption comes from your meters; energy consulting, the business case and funding questions stay with the specialists. TEEPTRAK is not an MES: it provides the state data that make the hours without production visible. TEEPTRAK is used in more than 700 plants in over 30 countries.
Further reading
- Energieeffizienz im Maschinenbau: Hebel & Wirtschaftlichkeit (dswerk.de, Dipl.-Ing. Dražen Stjepić, in German)
- Energy performance indicator in manufacturing: measuring kWh per part and energy used during downtime
- Compressed air consumption during downtime: matching machine states with utilities
FAQ
Why is rated power not enough to prioritize energy saving measures? Because it says nothing about time. The energy used without production depends on how many hours a machine waits, changes over or stays in standby, and that varies widely from one machine to another.
Do I need a separate sub-meter on every machine? For the largest consumers, yes, as dswerk.de recommends. For prioritization, it is often enough to determine the power per state properly once and then track the measured hours per state continuously.
Which measures usually come first? Often the ones that need no investment: shutdown routines for nights and weekends, energy saving modes during waiting time and isolating utilities. Investments in drives or hydraulics follow, with a payback calculation based on the measured hours.
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