Appendix
Description of Units
Activity data units are the quantities you multiply by an emission factor — kWh, passenger.km, tonnes, litres, and spend. Prefer physical units from meters and invoices over spend whenever you can; spend-based factors sit at the bottom of the data hierarchy and carry more uncertainty into the footprint.
A reference for the units used across the Activity Data Guide. Choose the most specific unit available for each activity, then apply the matching factor in Compare Your Footprint.
Energy
Use kWh for electricity and most grid-linked energy. Btu, mmBtu and scf appear on gas and some fuel lines where meters report in those units. Convert only when necessary — keep the unit that matches the invoice or meter so the factor lookup stays exact.
- kWh
- Btu
- mmBtu
- scf
Distance & transport
km covers vehicle distance; passenger.km is the standard for people travel (air, rail, road); tonne.km is used for freight. Prefer distance-based units over fuel volume when you have them — they usually map more cleanly to published factors.
- km
- passenger.km
- tonne.km
Mass & volume
kg and tonne cover materials, waste and many purchased goods. litre and m3 are used for fuels, water and some process inputs. Bin: 1100 litre is a waste-container volume used when weight is unknown. Mass is usually preferred over volume for solids.
- kg
- tonne
- litre
- m3
Digital
GB, Minute, vCPUh and TBh support IT and cloud activity data when you measure digital services rather than on-site energy. Use these only when the activity is digital infrastructure or usage — office electricity still belongs in energy units.
- GB
- Minute
- vCPUh
- TBh
Other
Unit, room.night, FTE.hour and HCM are activity-specific counts. tCO2e appears when you record a pre-calculated emission quantity. $ Spend and £ Spend are last-resort units when physical activity data is unavailable — expect higher uncertainty and document the estimate.
- Unit
- room.night
- tCO2e
- £ Spend
Frequently asked questions
- Should I prefer kWh or spend for electricity?
- Prefer metered kWh whenever you have it. Spend-based electricity factors are useful for gap-filling but sit lower in the data hierarchy and can distort intensity metrics year to year.
- When is passenger.km better than litres of fuel?
- For business travel and commuting in third-party vehicles, passenger.km (or km) usually matches published transport factors more closely than fuel purchases. Use litres only when you fuel owned or controlled vehicles yourself.
- Are spend units acceptable for SECR or GHG Protocol inventories?
- They are allowed as estimates when primary data is missing, but both SECR-style reporting and GHG Protocol guidance expect you to improve data quality over time. Flag spend-based lines clearly in your methodology notes.
Activities that use these
Activities that use these
- ElectricityElectricity activity data is the energy purchased from the grid or generated on site (for example solar PV) and consumed at facilities the organisation owns or has operational control over. It includes electricity used in offices, warehouses, data centres and manufacturing sites, but excludes electricity consumed by tenants in space you lease out. Ownership and control boundaries should follow the same consolidation approach (equity, financial control or operational control) used elsewhere in your inventory.
- GasGas activity data is the volume or energy content of mains natural gas combusted in equipment owned or controlled by the organisation, such as heating systems, cookers and industrial burners. It excludes gas consumed by tenants in leased-out space and excludes bottled propane, butane or other non-piped gases, which are tracked separately. Ownership follows the same operational or financial control boundary applied to the rest of your Scope 1 sources.
- Business travel: AirBusiness travel air is flight activity undertaken by employees for work purposes, booked either on commercial airlines or on aircraft the organisation owns, leases or charters. It includes domestic and international flights, short-haul and long-haul, but excludes an employee's regular commute to their usual workplace. Ownership of the aircraft — third-party commercial carrier versus organisation-operated — determines whether the flight sits in Scope 1 or Scope 3.
- Freight: Upstream: Third partyFreight: Upstream: Third party covers the inbound transportation and distribution of goods you've purchased, before they arrive at your site, where the movement is carried out by a carrier neither owned nor controlled by your organisation. It falls under Scope 3 Category 4 (Upstream Transportation and Distribution). This includes freight paid for by you directly and, where it's material and available, freight your suppliers pay for and pass through as an embedded cost — the boundary depends on your organisation's chosen reporting approach.
- Waste: AverageSpend-based average waste activity data, used as a proxy when an organisation cannot obtain weight or material-specific waste data (for example, tonnes of metal, paper, plastic or construction waste). Reported in £ or $ of waste-related spend rather than physical quantity.
- Information technologyInformation technology covers IT hardware, telecoms equipment and related purchased goods and services used by the organisation — laptops, tablets, smartphones, monitors, routers and IT services such as software development or data hosting — beyond the generic computer purchases tracked separately. It's reported under Scope 3 Category 1, and because the taxonomy holds device-specific factors for many named products, it rewards asset-register-level detail rather than blended spend.