Huntly is the only transmission connected coal plant in New Zealand.
According to the Electricity Authority stats for distributed generation...
There is no fuel type on the registry for Coal. "Other" has 120MW from 28 connections and "Undefined" 0.022 MW from 10 connections. From that it is safe to say that there is probably no other coal plants in operation in New Zealand. ( Source )
1. The New Zealand Government has not banned coal plants but they are hard to run economically against hydro, gas and geothermal.
2. Huntly was originally going to close sooner (end of 2018 when its current fuel stock ran out), it is only being kept open because other electricity companies are paying for the 2 units left to remain on call.
3. Huntly can be switched over to run on gas, which it mostly did until the 90's when gas supplies became tighter.