We protoyped a set of energy indices that can be used to assess, classify and compare any worldwide climate (weather data or extrapolated climate change data) to understand its energy burden on buildings and for the use in sustainable building design. The indices are intended as rapid and interactive holistic design tools applicable to any building type, with any design strategy, in any location worldwide and for the simple quantification of the impact of climate change on building energy use over its lifecycle. The indices are based on the fact that climate underlies building energy use and it is therefore possible to compare designs relative to climate, visualize where design emphasis needs to be placed and directly and interactively track the effect of design strategies. We then test them against the well-known Mahoney's table as well as against other parametric simulation software to evaluate their robustness and applicability in a wide variety of climatic contexts from around the world. The index works well in most climates except hot, humid ones. Lessons for future development and implementation are discussed. (C) 2012 Elsevier B.V. All rights reserved.