The requirements for installing a heat pump
You do not require a qualified and registered person to install the heat pump.
You do require an certified electrician (licensed electrical worker) to connect the unit to the electrical supply. Once complete, you should receive an Electrical Certificate of Compliance and Electrical Safety Certificate post installation.
In most cases, especially residential, installing a heat pump doesn't require a building consent.
For installation guidelines, see the Good Practice Guide from Energy Efficiency and Conservation Authority.
Heat pump water heaters do need consent, read about Solar and heat pump water heaters.
Penetration through an exterior wall
Making a penetration through the building envelope increases the chance of incoming moisture.
Most external walls are load bearing, and the position of the penetration should be considered carefully.
Prior to undertaking any work involving external wall penetrations, you should seek professional advice from a competent person.
For other building code compliance references, visit the Building Performance website.