The energy performance of heritage buildings is attracting growing interest in research and practice. Accordingly, as shown by our literature review, increasing numbers of articles on energy-efficiency measures for heritage buildings are being published in peer-reviewed journals. However, there is no overview of how energy efficiency and heritage conservation have been approached in the studies. To address this gap we categorized and assessed the identified studies in terms of two key elements of such investigations: energy analysis and analysis of cultural heritage values. Most of the studies evaluate and propose measures to reduce the operational energy use of single heritage buildings, and fewer have applied a broader system perspective. Moreover, the underlying notion of the buildings’ cultural heritage values seems to have been derived mainly from international conventions and agreements, while potentially significant architectural, cultural and historical factors have been rarely discussed. Our findings highlight that, when considering energy improvements, cultural heritage values should be more explicitly articulated and analysed in relation to established conservation principles or methodologies. Besides further scientific study, this point to the need of designing best-practice approaches that allow transparency and knowledge sharing about the complex relationships between energy efficiency and heritage conservation of buildings.