By identifying buildings with poor thermal performance and prioritizing these in terms of energy efficiency potential, a sustainable transformation of the building stock may be accelerated. However, there is currently a lack of thermal characteristics (TCs) differentiating total energy use from hot water circulation (HWC), hot tap water (HTW) and space heating in large building portfolios. This research demonstrates a methodology based on a change-point model for identifying and prioritizing TCs, which also enables prediction of the Comparative Energy Efficiency Potential (CEEP). The change-point model allows for the differentiation of various processes, i.e. space heating, HWC and HTW, using only heating supply data and outdoor temperature. The studied district consists of 70 multi-family buildings in the Vasastaden district in Linköping, Sweden. The findings demonstrate that the proposed methodology allows for identifying and prioritizing TCs connected to HWC, HTW and space heating. The highest CEEP is in space heating, corresponding to a maximum of 2,016 MWh (16% of the district’s energy use), followed by HWC, 699 MWh (6% of the district’s energy use) and HTW, 520 MWh (4% of the district’s energy use). Consequently, a total decrease of 3,235 MWh (26%) is made possible according to the studied energy efficiency targets.