What is a functional unit in LCA?
A functional unit fixes what a life cycle assessment (LCA) studies: what is delivered, how much, at what quality, and for how long. It is not merely a product's mass or count.
The reference flow is the amount of product, energy, or service activity needed for one functional unit. Every input, output, and impact relates to that basis.
Why does a functional unit matter to you?
A customer comparing products or services needs the same performance basis. A result per user can mislead if one software service provides more storage, availability, or time. An unclear unit also makes the calculation hard to reproduce.
How does a functional unit work?
Write what is delivered, how much, how well, and for how long. Identify the reference flow and inputs needed for one unit. Divide each environmental result by the number of functional units delivered.
What mistakes should you avoid?
- Using “one licence” without defining users, service level, capacity, and time.
- Comparing results based on different functions, quality levels, or lifetimes.
- Confusing the functional unit with the reference flow needed to provide it.
Is a functional unit the same as a declared unit?
No. A functional unit describes performance. A declared unit, such as one kilogram of material, may be used when an intermediate product's final function is unknown. It cannot make unlike products comparable.
Can you compare two LCA results with the same functional unit?
Not automatically. Check both studies cover the same stages and period, split shared inputs the same way, and calculate impacts the same way. Matching functional-unit wording is not enough.
What should you send with a functional unit?
Send its exact wording, reference flow, quality test, period, system boundary, and the calculation connecting activity data and results to one unit.