Net zero energy building (NZEB) is widely considered an effective solution to the increasing energy and environmental problems. Focusing on performance optimizations at single-building-level, conventional control strategies have not considered collaborations among NZEBs (such as renewable energy sharing) and thus optimal results may not be able to be achieved at a higher level, i.e. building-group-level. Few studies have evaluated the building-group-level performance of NZEBs using non-collaborative controls and researchers are still unclear about the performance improvement potentials if collaborative controls are implemented. Considering economic cost, load matching and grid interaction, this study aims to evaluate the performance of a group of NZEBs in which conventional controls are used. Meanwhile, associated performance improvement potentials are analyzed at building-group-level. The study results show that significant performance improvement potentials exist if NZEB collaborations are enabled. The study results also analyze the benefits of the NZEB collaborations in the three different aspects. To improve NZEB performance at building-group-level, new collaborative controls need to be developed to replace the conventional ones.