Linking energy performance certificates and real-world energy use in public buildings

Energy performance certificates (EPCs) play a central role in European building energy policy. Yet, differences between predicted and actual energy use—referred to as the energy performance gap (EPG)—continue to challenge their credibility and practical relevance. This study quantifies and explains the EPG in eight recently constructed municipal buildings in Norway, including schools, a care facility, a fire station, and a town hall.Using a mixed methods design that combines EPC recalculations with expert consultations, the study links measured deviations to technical and organisational factors. Seven of eight buildings used more energy than predicted, with an average deviation of 40%. Buildings with simple heating and ventilation systems and clear operational routines performed closest to expectations, while those with complex HVAC systems and continuous use showed the largest gaps.Consultations revealed that extended operating hours, control system inefficiencies, and fragmented contractor coordination contributed to underperformance, while early-stage operational follow-up helped reduce the gap. The results demonstrate that EPCs may substantially misrepresent real-world efficiency even in publicly owned buildings with integrated governance. This study provides new evidence on how design assumptions, system complexity, and management practices jointly influence energy outcomes, offering actionable guidance for more accurate modelling, commissioning, and post-occupancy evaluation.