In many cases, especially when data collection is limited or the production system is complex, detailed energy consumption per product or per machine is not available. In such situations, it is acceptable to use a simplified, “macro” approach to estimate energy use. Although this method introduces uncertainty, it is preferable to excluding energy impacts altogether.
1. Use Total Annual Consumption
When process-level data are missing, start from the total annual energy consumption of the site—electricity, gas, and other fuels combined. This value can usually be obtained from utility bills, energy reports, or corporate GHG inventories.
This mirrors the approach used in GHG Assessments, where total annual energy use is divided by relevant activity indicators (production volume, floor area, or operating hours).
If more granular data are available (e.g., monthly or per production line), use them to improve the precision of your estimate. The shorter the time scale and the closer the data to the actual process, the more accurate the allocation will be.
2. Allocate Energy Across Products
Once the total energy use is known, it must be allocated among the products produced on-site.
As explained in the previous section, the simplest allocation rule is to distribute energy based on each product’s share of total production output—by mass, number of units, or sales volume.
Example:
If the plant produces three products (A, B, and C) and product A accounts for 40% of total output, you can assign 40% of the total annual energy consumption to product A.
This assumption should be explicitly stated in your LCA documentation. It does not capture process-specific differences but provides a transparent and replicable estimation when no direct measurement is possible.
3. Document the Limitation and Plan for Refinement
This macro-allocation approach is not ideal, as it assumes all products require the same energy intensity. However, it remains valid when no other data exist—especially in early-stage assessments or scoping studies.
To improve accuracy later:
Request machine-level or process-level energy data from operators or technical teams.
Cross-check with energy meters, sub-metering, or equipment technical specifications.
Refine the allocation once these details become available.
4. Summary Recommendation
When specific process data are missing:
Start from total site-level energy consumption (annual or shorter period if possible).
Allocate this consumption across products using a macro indicator (mass, units, or sales).
Document the assumption and its limitations clearly.
Refine the estimate as soon as more detailed data become accessible.
This ensures that your LCA remains consistent and complete, while maintaining transparency about the level of data quality and uncertainty involved.