Abstract
Net-zero energy buildings produce enough renewable energy to meet their own annual energy requirements and have been proposed as an important method of reducing operational greenhouse gas emissions in the building sector. However, self-generation via building-integrated solar PV in cold and temperate climates is anti-correlated with increasingly-electrified heating demand and could increase seasonal variability in net electricity demand to the point that it poses challenges for future electricity systems. In this paper we explore scenarios of future large-scale uptake of electrically-heated, solar-PV net-zero energy residential buildings in New Zealand and quantify the seasonal variation of the resulting net electricity demand. A scenario of large-scale uptake of very high efficiency buildings leads to reductions in annual demand of -30% and seasonal variation of -50% in 2050 compared to a base case of current building standards. In comparison, a scenario with self-generation via solar PV without changes to the building standard reduces annual demand by -30% but increases seasonal variation by +40%. In a scenario where very high building standards are combined with solar PV, annual demand decreases by -65% and seasonal variation by only -4%. From a policy perspective, whether large-scale solar PV self-generation should be supported (in addition to very-high efficiency buildings) depends on an economic trade-off between the value of distributed solar generation (including any carbon emission reductions) vs the electricity system cost of seasonal variation. For New Zealand, given the low cost of renewable electricity from a variety of alternative sources, scenarios of large-scale uptake of solar-powered net-zero energy buildings are not favourable from an electricity system perspective.