This paper proposes a classification framework for energy efficiency evaluation tools by comparing 17 building energy performance assessment systems from ten countries. These systems include Energieausweis in Germany; the Ministry of Housing and Urban and Rural Development (MOHURD) rating in China; Energy Performance Certificates and Display Energy Certificates in the UK; and the Home Energy Rating System and ENERGY STAR in the U.S.

The unique assumptions and definitions underpinning these systems make it difficult to compare results–direct translation is nearly impossible. But
breaking apart the methodological characteristics of each approach enables the systems to be compared and studied.

Each system is evaluated by the approach to six basic underlying characteristics: energy consumption, energy type, building floor area, building type, performance scale, and energy uses. This framework reveals that the systems are diverse, and none of those studied uses the same methodology.

Upon further analysis it can be concluded that:

• Meanings behind common terms and concepts are poorly defined.
• Performance assessment systems are extremely flexible to local priorities.
• There is consistency in how to define energy quantification methods and energy types, but little consensus on how to define floor area or what energy loads to be included and excluded from assessment.
• It is still unclear how rating methodology and assessment structure affect the success of building energy performance.

Above all, there is a need for closer consideration of what energy efficiency connotes and its evaluation process. Increased understanding and transparency of precisely what is assessed and how it can help real estate investors, multinational corporations, policymakers, and researchers make more informed decisions based on what building energy performance scores truly mean.

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