From consumption to cost and CO₂eq

A meter measures kWh, cubic metres, litres. They are correct numbers and not very useful on their own: no meeting is held about kWh. Decisions are made on two derived quantities, cost and emissions, and obtaining them takes something more than the measurement.

Device properties

To each device IDA attaches some information that does not change over time, or changes very slowly:

• the energy carrier being measured: electricity, natural gas, water, compressed air, steam;
• the equipment's characteristics, such as nominal power, which say whether an observed consumption is plausible;
• the economic and environmental references valid for that carrier and that plant.

These are master data, not measurements. It is their combination with telemetry that produces the derived values.

What IDA computes

With the properties in place, measured consumption becomes:

• costs, per device, line, department or whole plant, over the same period the consumption is read on;
• CO₂ equivalent emissions, estimated on the consumption of the same perimeters;
• specific indicators, such as consumption or cost per Unit produced, when production data is available.

The economic references and emission factors applied depend on the carrier, the contract and the regulatory context of the installation: they are part of each plant's configuration, not a universal number, and they are defined together during the project phase.

Why cost per department changes decisions

A utility bill says how much the company spent. A cost attributed per line says where it spent, and that is the difference between an observation and a decision.

Attributing costs makes visible things that stay invisible in the total: a compressor working even with the plant stopped, a line whose consumption per Unit produced is double that of a twin line, a night-time consumption nobody ordered. These are items you can act on right away, and their effect shows up in the next measurement.

Why CO₂eq is not just a compliance exercise

Estimating the emissions associated with consumption serves two different purposes, both concrete.

The first is reporting: environmental certification paths and energy management systems ask for measured, traceable data over time, not annual reconstructions made after the fact.

The second, less obvious, is that a per-process emissions measure puts interventions in order of priority. Not all energy savings weigh the same on the carbon footprint, and seeing them side by side helps choose where to start.

What it takes for the numbers to be reliable

Derived quantities are only as good as the properties they rest on. Three precautions, valid in any project:

1. consistency of units of measure: a factor referring to one unit and a consumption measured in another produce a silent error, not a visible one;
2. updating over time: economic references change, and a cost computed on old values stays plausible while being wrong;
3. a declared perimeter: when comparing two departments, the two perimeters must include the same items, otherwise you are comparing different numbers that look the same.

None of these three can be guessed by an application. But if all three are in place, costs and emissions become part of the plant's everyday language instead of a report that arrives months later.