Energy 10 is a user-friendly energy simulation system that provides predictions of operating energy performance and identifies the most effective design strategies in reaching this performance level. A major advantage is that Energy 10 can be used from the very start of the design process throughout the design development. Energy 10 is developed by National Renewable Energy Laboratory, Lawrence Berkeley Laboratory, Sustainable Buildings Industry Council, Berkeley Solar Group and US Department of Energy (all in the USA). It is being continuously improved and now offers users an economical and highly effective simulation process for early design support. In June 2002 Energy version 1.5 was released. It is available through Sustainable Buildings Industry Council.