This paper investigates intetfuel substitution, separately accounting for different types of energy use in the U.K. manufacturing sector Econometric models of intetfuel substitution are applied to aggregate energy use, as well as to a specific energy use process-thermal heating-where intetfuel substitution is technologically feasible. Compared to the aggregate data, the estimated own-price elasticities for all fuels and the cross-price elasticities for fossil fuels are considerably higher for thermal heating processes. Nonetheless, electricity is found to be a poor substitute for other fuels based on both aggregate data and, separately, for the heating process. An increase in real fuel prices from the Climate Change Levy in 2001 resulted in higher substitution elasticities based on aggregate data, and lower substitution elasticities for the thermal heating process. The results of a counterfactual decomposition of change in the estimated elasticities indicate that technological change was the major determinant of the differences in observed elasticities before and after the energy price increase. doi: 10.5547/ISSN0195-6574-EJ-Vol33-No1-1