Energy Academy
Level 1/Carbon Accounting Fundamentals
Building & Reporting a Footprint9 / 11

Building Your First Footprint

From energy bills to a defensible number: boundary, data collection, a worked 200-tonne company footprint, and the screening approach that tames scope 3.

11 min read · Jacob Willis, Net Zero Lead · Last reviewed July 2026

Everything so far becomes real the first time you build a footprint, and the encouraging secret of this lesson is how quickly a defensible scopes 1+2 inventory falls out of data an energy-literate organisation already holds. The bills are the raw material; the scopes sort them; the factors convert them; the Protocol's choices frame them. This lesson walks the full sequence on a worked company, then covers the part that genuinely is hard, scope 3, and the screening mindset that stops it consuming you.

The sequence

  1. Draw the boundary. Choose the organisational approach (operational control, usually), list the sites and vehicles inside it, and write the choice down.
  2. Pick the period and base year. Twelve months, normally the financial year to match SECR; the first properly-measured year typically becomes the base year.
  3. Collect activity data. Electricity and gas from bills or (better) meter data; fuel-card litres for the fleet; refrigerant top-up records from the F-gas log, which double as your fugitive-emissions data.
  4. Apply the year's factors, sum by scope, and keep every line's source: the factors-lesson habits in action.
Worked example — a 200-tonne company, from three bills
Given
  • A distribution company (operational control boundary): 250,000 kWh electricity, 400,000 kWh gas, 30,000 litres of fleet diesel in the year
  • Factors (2024 set): electricity 0.207, gas 0.183 kgCO₂e/kWh; diesel ≈2.51 kgCO₂e/litre
Find
The scopes 1+2 footprint.

Scope 3: screen before you measure

Scope 3 is where footprints stall, because fifteen categories of other people's data cannot all be measured at once, and mostly should not be. The professional approach is screening: estimate every category roughly (spend-based factors, which convert £ spent per category into approximate tonnes, exist for exactly this), rank them, and let the ranking drive effort. A distributor discovers haulage and purchased goods dwarf everything; a services firm finds commuting and purchased IT; a manufacturer finds materials. Then improve data quality only where it matters: activity-based data (litres, tonne-kilometres, supplier-specific figures) for the top categories, spend-based estimates and honest labels for the tail. Completeness with graded accuracy beats false precision everywhere, and the Protocol's transparency principle blesses exactly that: state the method per category and upgrade over time.

Intensity: making the number comparable

An absolute footprint cannot be compared across years of growth or between organisations of different size, so credible reporting pairs it with an intensity metric: tCO₂e per £m revenue, per unit of product, per full-time employee. This is the platform's normalisation discipline wearing carbon units, spring flushes and all: the dairy course's warnings about production-driven ratios apply verbatim. SECR requires at least one intensity ratio for exactly this reason.

Start where the data is strong

A credible footprint is built outward from its best data: metered energy first (scopes 1 and 2, usually an afternoon's work for a single site), fleet fuel next, refrigerants from the F-gas log, then scope 3 by screening and ranking rather than by heroic measurement. Organisations that begin with a complete-but-graded inventory improve it every year; organisations that wait until they can measure everything perfectly are still waiting.

What's next

The number exists; now it goes to work. The final lesson covers reporting destinations (SECR, questionnaires, targets), the reduction-before-offsetting hierarchy, and how to make claims that survive the scrutiny this course has taught you to apply to everyone else's.

Sources and further reading