Investigations of a Cost-Optimal Zero Energy Balance: A study case of a multifamily Net ZEB in Denmark

The Net Zero Energy Building (Net ZEB) concept is worldwide recognised as a promising solution for decreasing buildings’ energy use. Nevertheless, a consistent definition of the Net ZEB concept is constantly under discussion. One of the points on the Net ZEB agenda is the zero energy balance, in particular the types of energy use that should be included in it. Since the user perspective and the cost of energy-efficiency technologies is so crucial for the successful adaptation of energy-conservation solutions, such like the Net ZEB concept, this paper has deployed the Life Cycle Cost (LCC) analysis and taken a view point of private building owner to investigate what types of energy uses should be included in the cost-optimal zero energy balance. The analysis is conducted for five renewable energy supply systems and five user profiles with a study case of a multi-storey residential Net ZEB. The results have indicated that with current energy prices and technology, a cost-optimal Net ZEB zero energy balance accounts for only the building related energy use. Moreover, with high user related energy use is even more in favour of excluding appliances from the zero energy balance.