Energy and economic analysis of building retrofit and energy offset scenarios for Net Zero Energy Buildings

The concept of Net Zero Energy Buildings is gaining momentum. However, the underlying idea of offsetting the energy drawn from the grids with local production is yet to be proven as economically efficient, namely when compared with alternatives such as district/ neighbourhood-level facilities or adding more large-scale facilities to the national grid(s). This paper presents a study on strategies for making an existing neighbourhood becoming net zero energy, focusing on the level of retrofit to apply to the buildings, on the proximity of the offset and on the selected offset equipment. The following discretization was considered: three levels of energy efficiency (low, medium and high), four offset generation alternatives (building integrated photovoltaic (PV), off-site large-scale PV, off-site largescale wind turbines and not offsetting) and two energy tariff types (subsidized and nonsubsidized). The results have shown that, under the reference economic conditions considered, it is best to upgrade the energy efficiency up to the medium level, and then offset the demand with off-site large-scale wind turbine equipment. These suggest that reaching net zero balance through on-site generation is less efficient than doing it through large-scale facilities.