This study assessed a range of simple energy efficiency opportunities across three building types (detached, attached and apartment), and three climate zones covering Australia’s largest population centres. It sought to identify improved energy efficiency measures for which the capital cost is outweighed by financial benefits ('cost-effective') from a societal perspective over the lifetime of the relevant building elements, in most cases a 10-15 year period. It considered opportunities to improve efficiency of the building ‘fabric’ (walls, ceilings, windows etc.) and fixed equipment (hot water, lighting), but not plug-in appliances, which are regulated separately. Results presented in this report are preliminary, and a number of improvement opportunities remain under investigation.