The energy balance is decomposed into energy demand activities and unit consumption, which is met by energy conservation and demand technologies. The overall purpose was to provide a flexible and easily understandable tool for translating energy demand forecasts into their economic and environmental consequences. The model was used for the Danish energy planning during the 1980s, and the methodology was tested in other counties. The modelling tool was rewritten for spreadsheet software to be used for the Danish energy and environmental planning 1990 and 1996 (the BRUS model). This is a technical economic model with an integrated treatment of energy demand and supply which allows for the calculation of demand driven scenarios for tyhe reduction of CO2. The methodology and general model structure are applicable to other national or regional systems.