Hybrid-electric vehicles have experienced a significant rate of growth in the last 10 years. This is remarkable, since the automotive sector is typically averse to the more radical technological change of engines. The internal combustion engine has been around for more than 100 years after all.In this paper we describe and explain the emergence of electric engines in the automobile market after 1990. We explicate the role of techno-economic mechanisms alongside social and regulatory mechanisms (including the social meaning of an engine). The co-evolutionary analysis is novel in the integrated conception of actor perspectives, feedback effects and competition between products. We find three sources of lock-in through path dependency: from de...