Part of the difference between countries' price responses may be explained by the differences in prices and existing taxation in different countries (Hoeller and Coppel [13] ). In order to assess the magnitude of this effect, an ad valorem tax scenario was constructed in which the same percentage rate of tax is levied in each country, at a level giving the same total revenue overall, in the proportions on each fuel as for a 50/50 carbon/energy tax in the UK. This translates to 20.8% on oil, 28.47% on gas and 83.95% on coal.