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Heat pumps in SouthlandSized for frost, damp air and the westerlies.

Invercargill needs more heating than any other city on this site: NIWA's Southland table gives it 2,994 heating degree-days a year, more than Queenstown's 2,813 or Dunedin's 2,559. Winter air here is cold and humid, so outdoor units frost over and defrost often. A Southland heat pump has to be sized for that, and sited out of the worst of the westerly gusts.

What's different about heating in Southland

A heating season with a July peak

In NIWA's degree-day table (base 18 degrees), Invercargill Aero's heating total of 2,994 a year includes 398 in July alone, with only 8 on the cooling side. Cooling isn't a Southland job.

Climate zone 6

MBIE's H1/AS1 energy efficiency Acceptable Solution (sixth edition, published 27 November 2025) places Invercargill City in zone 6, the last of New Zealand's six building climate zones.

Below zero on 41 days a year

NIWA says Invercargill's minimum drops below 0 degrees on 41 days a year on average, and the lowest it has recorded is -9.0 degrees. NIWA's 1991 to 2020 normals put the July mean daily minimum at 1.1 degrees.

Humid winter air

Invercargill Aero's mean 9 am relative humidity is 85% across the year and 89% in June and July. Mitsubishi Electric NZ says the more moisture in the air, the more freezes on the outdoor coil.

Wind off Foveaux Strait

Gusts pass 61 km/h on 109 days a year and 94 km/h on 15, NIWA says, and the city gets a relatively high share of strong westerlies, partly channelled through Foveaux Strait.

Airsheds and burners

The Otago Daily Times reported in September 2026 that Environment Southland's Regional Air Plan, adopted in 2016, phased out older non-compliant burners and banned open fires in the Invercargill and Gore airsheds. Non-compliant burners installed between 2010 and 2014 are banned from 1 January 2034.

LPG, not mains gas

Te Waihanga says distributed gas is only available in the North Island, so any gas heater in Southland runs on LPG.

What it means for a heat pump job

Most Invercargill homes already heat this way. At the 2023 Census, 79.63% of Invercargill City homes used a heat pump as a main type of heating, and Environment Southland credits more heat pumps, among other factors, for the fall in PM10 exceedances that left 2026's record clean.

For a new unit, the 2 degree heating figure on the Zoned Energy Rating Label matters more than the headline one. EECA says that where nights reach 2 degrees or less, capacity at 2 should match or beat capacity at 7. Tenancy Services' heating tool guide also warns that some heat pumps struggle just above freezing.

Outside, the unit needs shelter, clear air around it and solid fixings. BRANZ says outdoor units should be stable, which matters on a site that takes regular gusts.

The national rules in Southland

A registered and licensed electrical worker must connect the heat pump, since it's prescribed electrical work. Expect a Certificate of Compliance no later than 20 days after the work, plus an Electrical Safety Certificate to keep for at least 7 years.

No building consent is needed for a pipe hole up to 300 millimetres across through an existing house (Schedule 1 of the Building Act), but the Building Code, district plan noise limits and any body corporate rules still apply. We don't hold a verified position for Southland's councils, so ask yours if your install is out of the ordinary.

For rentals, Tenancy Services says its heating assessment tool allows for things that make a home easier or harder to heat, such as being in Southland rather than Northland. Warmer Kiwi Homes is EECA's programme for owner-occupied homes, and since 9 January 2026 EECA hasn't accepted new burner applications, which matters if a 2034 deadline is coming for yours.

What we'd do

If it were our Southland home

We'd treat the 2 degree heating figure as the heat pump's real size, and we'd want the outdoor unit on a sheltered north-facing wall if the house allows it. If a burner put in between 2010 and 2014 does the heavy lifting, we'd ask Environment Southland whether it's compliant well before 2034. Installers who specialise in heat pumps for cold sites then see the job, and only the one who takes it gets your details.

Cities in Southland

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Read next

  1. 01Heat pumps in InvercargillHeating an Invercargill home with a heat pump: frost, humid air, wind, burner rules and sizing.
  2. 02Heat pump installation in InvercargillInstalling a heat pump in Invercargill: sizing for frost, outdoor unit placement, sign-off and quotes.
  3. 03What size heat pump do I need?How to work out the kW for a room, and why the 2 degree figure on the label matters.
  4. 04The healthy homes heating standardWhat the rental heating standard asks for, which heaters count, and how to check a heat pump against it.
  5. 05Warmer Kiwi Homes heat pump grantsWho EECA's programme is for, what its current heat pump list covers, and how to check before you sign.
  6. 06Heat pumps compared with other heatingHow a heat pump stacks up against a wood burner, gas, electric heaters and central heating.

Where this information comes from

We don't publish prices. Every home is different, so an installer's written quote is the only real number. How we write and check these pages.

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