In energy studies, decomposition analysis is a methodology used to decompose an energy aggregate or an energy-related environmental aggregate whereby the effects associated with several meaningful factors can be quantified. The basic models include those formulated using the Laspeyres, Paasche and Marshall-Edgeworth indices. We describe three extended decomposition models developed through refining these three basic models. It is shown that these three extended models give exactly the same decomposition results and they, together, can be treated as all exact decomposition model. A numerical example on energy-related CO, emissions in Europe Union is presented.