What Christchurch changes about a heat pump water heater
A frost most July nights
NIWA's figures for Christchurch average 19 ground frosts and 11 air frosts in July, with June and August not far behind. Flat ground where cold air can't drain away on still nights gets frost most, and much of the city is flat.
Ripple control in the same months
Orion only runs its hot water control periods between 1 May and 31 August, the frostiest stretch of the year. Ask your retailer and installer how a heat pump unit will be supplied, and whether it sits on a controlled plan.
Outdoor units are already familiar
At the 2023 Census, 86.2% of Christchurch homes used a heat pump to heat rooms. So many sections already carry an outdoor unit for room heating, and a water heater needs a clear spot of its own.
LPG bottles need clearance
With no piped natural gas in the South Island, some homes run LPG. Rockgas counts heat pumps among the ignition sources its bottles must be kept a set distance from, so the two can't simply share a corner.
How it copes with the cold
Rheem describes its heat pump water heaters as having a storage tank much like an electric cylinder, plus an electric back-up element for when the outdoor air gets really cold. On a still, frosty morning, that element may be doing more of the work. Ask the installer how the back-up is set up and when it switches in.
Rinnai sums up an install as needing three things: a licensed plumber, an electrician and a suitable site. Ask what makes a site suitable at your place: the outdoor space, room to service the unit, and how far the hot water then travels to the taps. Our brand guides say what each maker offers.
Heat pump against what Christchurch homes usually have
| How it works here | Worth checking | |
|---|---|---|
| Heat pump water heater | Warmth from outdoor air into a tank, with an electric back-up element | Outdoor space, frost exposure, and whether the cylinder has to move |
| Electric cylinder | An element heats stored water, often on Orion's ripple control in winter | Your electricity plan before you blame the cylinder |
| LPG storage or califont | Bottled gas, since there's no piped natural gas here | Bottle position, flue and the gasfitter's certificates |
| Wetback cylinder | Heated by a wood or pellet fire, with an element for the rest of the time | The stricter consent exemption that applies to wetback cylinders |
Consent and who does the work
A heat pump water heater is still a water heater under the Building Act. Replacing a cylinder with one, or moving it, is exempt from building consent when the new heater includes, or is connected to, a controlled heat source and an authorised person does the work (Schedule 1, clause 38). The Act doesn't define 'controlled heat source', so ask the installer or the council how your model fits. Exempt or not, the result must meet the Building Code.
The plumbing must be done by someone authorised under the Plumbers, Gasfitters, and Drainlayers Act 2006, and an electrician does the electrical connection. If your old cylinder runs off a wetback, swapping it for a heat pump isn't the like-for-like change that clause 37 covers, so check the consent position first.
Prices, savings and subsidies
We don't publish prices or savings figures; the percentages in advertising are the makers' own. We couldn't confirm any current scheme that funds heat pump water heaters in Christchurch.
Questions for the installer
- Where would the unit sit, and how frosty does that spot get?
- How does the back-up element work on a July morning?
- Will it be on a controlled electricity plan, and what does that mean in winter?
- We have LPG bottles: where can the unit go so both stay compliant?
What we would do
Get the site looked at in daylight, with the installer and you both standing where the unit would go. In Christchurch, pick a spot that isn't the coldest, stillest corner of the section, keep it clear of any LPG bottles, and ask for the back-up element and the electricity plan to be explained before you choose a model.