The most recent official loneliness survey of the New Zealand population was undertaken by Stats NZ as part of the General Social Survey 2018. They found that 3.4% of the population aged 15+ feel lonely most/all of the time in the last four weeks, and another 13.0% feel lonely some of the time.
Adjusting for the most recent Stats NZ 2019Q4 provisional NZ population estimate, this equates to 656,000 New Zealanders aged 15+ feeling lonely some/most/all of the time in the last four weeks (see figure).