Efforts to contain and reduce greenhouse gas emissions from energy will always depend on what climate-friendly technologies are available. Energy models are playing an important part in helping policy makers set emission targets. Making energy models more transparent will be important in developing realistic, achievable and cost-effective climate policies. This workshop, whose purpose was to improve understanding of the energy technology assumptions used in energy models, included experts responsible for several of the key models being used by IEA Member countries and the European Commission.