Within the carbon reduction commitment, energy consumption is divided into 'core sources' and 'non-core sources'.

Core sources will typically include all electricity and non-transport fuel those provided as a constant supply and invoiced on a regular or monthly basis. It will be mandatory for all organisations to report their core sources of energy,

Non-core sources will generally include more ad hoc energy supply, including some bulk fuels. Organisations will only be required to record their non-core sources if they are unable to identify a minimum of 90% total carbon emissions from the core sources.