This note GEN22, was originally published in November 1998, and reviewed by Graham Treloar and Roger Fay in September 2003. This paper is now considered out of date and will be republished in due course. In the meantime, please consider the issues below. Energy use is a widely used measure of the environmental impact of buildings. Recent studies have highlighted the importance of both the operational and embodied energy attributable to buildings over their lifetime. The method of assessing lifetime building energy is known as Life-Cycle Energy Analysis (LCEA). LCEA is an easily conducted form of Life-Cycle Assessment (LCA) and one which is particularly relevant to the building industry due to energy efficiency efforts over the last few decades. LCA forms part of the ISO 14 000 series of standards on environmental management and is covered by the ISO 14040 group of Standards. In summary, a building’s life-cycle energy consists of its initial embodied energy, its recurrent embodied energy and its operational energy over its lifetime. These terms are defined below. There are powerful environmental reasons to use LCEA as a decision making tool at the design development stage. Proper application of LCEA can result in substantial net reductions in energy use over the projected life of the building. With federal environmental initiatives driven by Kyoto target obligations necessitating quantification of greenhouse gas emissions at the national level, it seems increasingly probable that analyses of this kind will increase in use. This note briefly explains some of the theoretical issues associated with LCEA and then uses a case study to demonstrate its use in evaluating alternative design strategies for an energy efficient residential building.