I would guess dankelflaute is mostly irrelevant in New Zealand because our hydro lakes (assuming rivers are flowing) can smooth out generation shortfalls shorter than say a month (kinda equivalent to pumped hydro or batteries). A 3 day dankelflaute as given in the Wikipedia example would likely not matter in New Zealand. Plus our weather is variable, and generation is spread out.

  New Zealand's hydro storage is less than a sixth of the country's total yearly electricity use. Hydro generation typically accounts for over 50% of our annual electricity generation, making us reliant on river flows. The maximum storage (full lakes) is around 5 TWh.

About 20% of New Zealand electricity comes from geothermal. I would guess political and environmental issues would dominate costs for increasing geothermal generation (plus I would assume we've taken all the low hanging fruit).

https://en.wikipedia.org/wiki/Dunkelflaute