We seem to have been having them for a while now, every winter there are concerns about brownouts. The Electricity Authority put it into plain English on their website - winter sees the highest demand for electricity, obviously, also when it's unseasonably cold in autumn or spring, that can cause high demand periods. The winter peak capacity reflects the ability of the electricity system to meet high winter demand. So typically, solar doesn't produce electricity during peak demand periods in winter because it's dark. Wind generation, which is 10% of New Zealand's electricity generation capacity and growing, isn't reliable because, who knew, but cool temperatures bring low wind speeds. So solar is out, wind generation is out during winter.
