A technological stock model of private car energy demand is built, using as explanatory

variables, fleet structure, the profile of activity, and fleet efficiency. Disaggregating the

three variables by vehicle technology and age produces a detailed profile of private car

activity and energy consumption, giving accurate energy calculations and allowing detection

of the technological drivers of energy consumption. Methods for calculating fleet onroad

energy efficiency in terms of an on-road factor are developed. The methodology is

applied in an Irish case study and results show a 37% increase in private car energy demand

between 2000 and 2008, and that driving this increase was a growth in diesel and larger

engine activity and the ageing of the fleet.