We examine the diffusion of steam technology across British counties during the eighteenth century. First, we provide new estimates for the regional variations in the timing, pace and extent of usage of steam engines. Our main data source is an updated version of the list of steam engines erected in Britain during the eighteenth century originally compiled by Kanefsky and Robey (Technol Cult 21:161-186, 1980). Following a rather established approach for analysing the diffusion of new technologies we fit S-shaped growth functions to the data on the numbers of steam engines installed in each county. In this way, we are able to provide a comprehensive appraisal of the relative speed of the diffusion process in different counties. Second, in order to assess the relative importance of the variables shaping the diffusion of steam power technology, we study the relationship between the number of steam engines installed in each county and localization factors such as coal prices, availability of water sites, number of textile mills and number of blast furnaces.