Whereas the need to mobilize investment in energy supply technologies is broadly understood, with the current level of investment estimated in the order of $0.7-0.9 trillion a year, there is a notable absence of analogous investment data for end-use technologies. This paper presents a global, bottom-up estimate of total investments in end-use energy technologies based on volume data and cost estimates for 2005. Total investment in end-use technologies was conservatively found to be in the order of $0.3-4 trillion depending on the definition of end-use technology used.