The recast of the European Performance of Buildings Directive (EPBD) requires the uptake of a definition of so called ‘nearly zero energy’ buildings (nZEB). Belgium was first to set a definition for a ‘net zero energy house’ (NZEB) in 2009. Every year the definition is revised for consistency with shortcomings and emerging issues. The Belgian definition raised many questions regarding (1) the net balance, (2) the application and calculation method (3) the indoor air quality and comfort, (4) energy use included in the balance, (5) the type of buildings, (6) the accepted renewable energy supply options, (7) the quality assurance and monitoring and (8) energy storage and the connection to the energy infrastructure. Therefore, the paper presents a review on the current Belgian definition and its market status in comparison with the international context. The aim of the paper is to review current definition discussions and pave the way to a more consistent definition.