Ashburton's climate, rules and homes
Frost more often than Christchurch
NIWA gives Ashburton an average of 51 days a year below 0 degrees, against 34 at Christchurch. Wikipedia's table of NIWA's 1991 to 2020 normals puts the July mean minimum at 0.5 degrees.
Hot summers as well
Ashburton has reached 41.3 degrees and averages 39 days a year above 25 and 7 above 30. On those days a heat pump on cooling earns its keep.
Burners in over half of homes
In the 2023 Census, 52.65% of Ashburton District homes used a wood burner and 73.85% a heat pump; 28.06% used an electric heater and 1.86% a pellet fire. Homes can use more than one type.
A Clean Air Zone
Environment Canterbury says low-emission wood burners can no longer be installed in its five Clean Air Zones, and Ashburton is one of them.
Climate zone 5, and no piped gas
MBIE's H1/AS1 puts Ashburton District in climate zone 5. The South Island has no reticulated natural gas, so gas heating means LPG bottles.
The town
Ashburton sits on the Hakatere, the Ashburton River, 85 kilometres south-west of Christchurch. It had 20,346 residents in 8,124 dwellings in 2023, a median age of 43.1, and the postcode 7700. The council is Ashburton District Council.
Why Ashburton heat pumps need to be chosen carefully
Output falls with the temperature. BRANZ says air-to-air heat pumps lose efficiency below 6 to 7 degrees, though some models still heat down to -15. Its H3 rating shows output at -7 degrees, and EECA's label shows it at 2. On a night near freezing, those numbers matter more than the headline one.
Frost means defrost. EECA says below 5.5 degrees outside a heat pump has to divert some heating to defrost its outdoor coil. That's normal. Give the unit open air and a drain for the meltwater, and don't box it in under a deck.
Replacing an old burner. With low-emission burners off the table in the Clean Air Zone, the choice is usually a heat pump or an ultra-low emission burner. Our comparison with other heating weighs them up, and the Christchurch repairs page covers a unit that gives up in a cold snap.
What we'd do
If we were heating an Ashburton house
We'd pick the heat pump on its cold-weather output and ask the installer for the figure at 2 degrees, or at -7 if the brand publishes it. We'd put the outdoor unit on a north or west wall, which BRANZ says is the warmest spot for heating performance. And with a burner near the end of its life, we'd get the heat pump quoted before deciding on a replacement.