The Reference Approach (RA) is a top-down approach, using a country’s energy supply data to calculate the emissions of CO2 from combustion of mainly fossil fuels. The methodology is relatively simple in comparison to the more complex sectoral approach methodologies. The simplifications and assumptions used in the RA can mean some outputs of the calculations are not always intuitive. However, the outputs of the RA can be understood if we consider how the calculations work. Part of this involves a separation of primary and secondary fuels, where only the production of primary fuels are included, as secondary fuel production are assumed to be captured in primary fuel production, and there is no deduction from fuels for transformation into other fuels. This means that countries with primary fuel production and fuel transformation may have large ‘apparent consumption’ of primary fuels even though crude oil is not used as a fuel, and conversely secondary fuel use can have a negative ‘apparent consumption’ if a large proportion is derived from other products that are transformed into a secondary fuel within the country.