Energy demand drives the whole energy system. It impacts the amount of energy used, the location where it used, the type of fuel used and the technology that is used. Using energy efficiently is of critical importance for meeting the world'€™s energy needs in a sustainable and affordable way. To successfully model reliable energy scenarios a detailed quantifiable understanding of the energy demand technologies is required. Such well documented detailed quantifiable understanding is already available, to the IEA-ETSAP community, for many energy demand technologies and more technologies are added to the list regularly.