Specific energy consumption
Specific energy consumption (SEC) is the energy a plant uses per unit of output: kWh per tonne, MWh per hectolitre, kWh per thousand units. It is the most common energy performance indicator in manufacturing and the easiest to misread, because a large base load makes the ratio fall whenever volume rises, whether or not anything became more efficient.
Definition
Specific energy consumption is total energy consumed over a period divided by the output produced in the same period. The energy can be electricity, fuel, steam or any metered utility; the output is whatever the plant counts: tonnes, litres, cases, bags. Water, compressed air, carbon dioxide and any other metered input can be expressed the same way, which is why Augos uses the broader term resource intensity for the family and SEC for the energy member of it. SEC is an intensity, so a lower figure is better, and it only means something when the boundary (which meters, which lines) and the period are stated with it.
Source: ISO 50006:2023, energy performance indicators and energy baselines; Glossary: specific energy consumption
The formula
SEC = energy consumed ÷ units produced, over the same period and boundary.
A plant that draws 11,493 kWh in a month and produces 2,567,797 units has an SEC of 4.48 kWh per thousand units. Nothing is wrong with the arithmetic. The problem is what the single number hides, which the next section shows on real data.
A real month
One anonymised flexible-packaging plant, one month in 2026. Electricity from the site's mains meter; output from the production counters on its lines, in bags.
| Period | Electricity and output | SEC |
|---|---|---|
| Whole month | 30 days · 11,493 kWh · 2,567,797 bags | 4.48 kWh per 1,000 bags |
| 1 to 18 Sep | 14 production days · 8,270 kWh · 1,793,188 bags | 4.61 kWh per 1,000 bags |
| 21 to 30 Sep | 6 production days · 2,274 kWh · 774,071 bags | 2.94 kWh per 1,000 bags |
| Idle days | 10 days · 949 kWh · 0 bags | undefined |
The plant produced the same amount per day in both production periods, about 128,000 bags, yet its SEC fell by 36%. Nothing about the bags changed. Daily electricity fell from 591 kWh to 379 kWh because less equipment was running for the shift; the data does not say what, and this page does not guess. A monthly SEC report would have shown a 36% efficiency gain and been wrong about the cause. The ten days with no output used 949 kWh between them, about 4 kW around the clock, which the ratio cannot express at all because its denominator is zero.
Source: Augos platform, one anonymised flexible-packaging plant, mains electricity and production counters, a 30-day month in 2026
Why the ratio misleads
Every plant has a base load: lighting, compressors, chillers, extraction, servers, the standing draw of machines switched on and waiting. That load is paid for whether the line makes one unit or a thousand. When output rises, the base load is spread over more units and the SEC falls; when output falls, the SEC rises. The ratio therefore reports volume as if it were efficiency. ISO 50006 names this directly: a ratio indicator assumes a zero-intercept relationship between energy and output, and in a plant with a base load that assumption is false. The standard's answer is a model-based indicator, energy as a function of output with the intercept estimated from data, which is the subject of Fixed and variable energy.
The second way the ratio misleads is the boundary. A plant that reports kWh per tonne for one line while the compressor house serves four lines is comparing apples with part of an orange. Augos measures at site level first, total site resource against total site production, for exactly that reason, and the module that does it is described on Utility and Resource Intensity.
Source: ISO 50006:2023 on ratio and model-based indicators; monitoring and targeting practice (Bureau of Energy Efficiency, India, energy monitoring and targeting guide)
Three kinds of indicator
ISO 50006 describes three kinds of energy performance indicator. A measured value, such as monthly kWh, says how much but nothing about output. A ratio, such as kWh per tonne, normalises for output but inherits the base-load problem above. A model, such as energy = base load + slope × output, separates the fixed draw from the variable draw and lets a plant compare months at different volumes honestly. The right indicator depends on how large the base load is relative to the variable load; the packaging plant above is an extreme case, where almost all the electricity is operating base load and the per-bag component is small.
Published ranges
Sector ranges exist and are useful as context, provided their boundaries are respected. The EU's Best Available Techniques conclusions for the food, drink and milk industries give indicative SEC ranges per tonne of raw material unless stated: market milk 0.1 to 0.6 MWh; cheese 0.10 to 0.22 MWh; milk powder 0.2 to 0.5 MWh; brewing 0.02 to 0.05 MWh per hectolitre; soft drinks and nectar or juice 0.01 to 0.035 MWh per hectolitre; grain milling 0.05 to 0.13 MWh; sugar 0.15 to 0.40 MWh per tonne of beet. Plastics processing is usually described as a fixed-plus-variable load (a base load plus kWh per kilogram processed) rather than a single ratio. No published South African sector ranges for food and beverage or plastics were found; a plant's own history, measured at the same boundary, is the benchmark that holds up.
Source: Commission Implementing Decision (EU) 2019/2031, BAT conclusions for the food, drink and milk industries; Kent, external benchmarking of injection moulding energy efficiency (Plastics Technology)
Common questions
What is specific energy consumption?
Energy used per unit of output over a stated period and boundary: kWh per tonne, MWh per hectolitre, kWh per thousand units. Lower is better, and the figure is meaningless without its boundary.
Why did our SEC improve when we did nothing?
Most likely because output rose, or because a fixed load was switched off for reasons unrelated to the product. A ratio spreads the plant's base load over however many units were made, so it reports volume as efficiency. A fixed-plus-variable model separates the two.
Is kWh per unit a Scope 3 figure?
Not by itself. It is the manufacturer's own Scope 1 and 2 activity data per unit. With emission factors and a stated boundary it becomes a product footprint, which is the customer's Scope 3 input. See Scope 1, 2 and 3 for a factory.
Does Augos publish SEC benchmarks?
No. Augos measures a plant's own resource use against its own production at half-hour resolution and compares it with the plant's own history. Published sector ranges are cited as context, with their boundaries.
Can the same method apply to water or compressed air?
Yes. Any metered input over counted output follows the same logic, and the same base-load caveat applies.