The energy performance certification (EPC) scheme, introduced in the European Union approximately 20 years ago, has become the focus of the upcoming revision of the Energy Performance of Buildings Directive (EPBD). Despite its widespread use, the current EPC scheme has several shortcomings that need to be addressed. The Energy flexible DYnamic building Certification (E-DYCE) project has developed a dynamic approach to address these issues. The methodology includes a dynamic assessment of a building’s energy needs and comfort conditions under standard and different from standard conditions of building use to support Performance Gap (PG) analyses. The E-DYCE approach includes a dynamic building performance simulation with comfort and energy-related key-performance indicators (KPIs) measured and calculated according to E-DYCE DEPC methodology. These KPIs can inform end-users about indoor environmental quality conditions decisive for building energy performance, aid building managers in detecting dysfunctions resulting in PG, and include energy performance indexes for heating, cooling, lighting, domestic hot water, and more. Overall, the E-DYCE approach offers dynamic, reliable, and customer-tailored information and optimization possibilities to end-users while potentially resolving known shortcomings of the existing EPC schemes.