Lack of new capacity is the real problem.
Also thanks to the Resource Management Act (RMA) no significant new capacity has been built in NZ for some time.
Hydro isn't particularly popular with the Greens either and NIMBY'ism has blocked a number of other alternatives.
If you don't build new generating facilities eventually demand growth catches up and you have to turn off the lights. This has already happened for much of the heavy use companies which are operating with reduced productivity.
NZ, clean, green and DARK!