b. Similarly, the first step for the Sectoral Approach is to collect actual consumption statistics by fuel type and economic sector (e.g., Public Electricity and Heat Production, Petroleum Refining, Manufacture of Solid Fuels, and Other Energy Industries).

c. The first step for a Tier 2 or 3 method is to collect actual fuel consumption statistics by fuel type, economic sector, and combustion technology type. Tier 3 methods use activity data (e.g., kilometers traveled) as a proxy to estimate fuel consumption or to estimate CO₂ emissions directly using emission factors.Tier 3 is generally used for estimating only non-CO₂ emissions, because in most cases using actual fuel data is more accurate for estimating CO₂ emissions.

d. The second step is the conversion of fuel data to a common energy unit. In the OECD/IEA Energy Statistics and other national energy data compilations, production and consumption of solid and liquid fuels are generally specified in tonnes and gaseous fuels in cubic meters.

For consistency purposes, original units (mass units) should be converted into energy units using net calorific values (i.e., heating values). Where available, different calorific values for production, imports, and exports in a country should be used.

For transparency purposes calorific values used for the conversion should be reported. Some countries may report gross calorific values due to national statistics systems.