The IEA refers to energy efficiency as the "hidden fuel. It provides all the benefits of a clean energy source, including improved energy security, environment, health and economic development - but by saving rather than providing energy. That is particularly important when it comes to development and developing economies, where rapid urbanization and economic growth often combine with particular difficulties in terms of network expansion and production. How we develop cities, communities, transport, and industry today will have major impacts on the ability to provide modern energy reliably and adequately.