Whangārei summers, by the numbers
Warm February afternoons
The 1991 to 2020 normals in Wikipedia's tables (citing NIWA) give a February mean daily high of 24.7 degrees at Whangārei Airport and 25.2 at the Whangārei City station.
Cooling is a real share of the year
NIWA's degree-day table, which measures the energy needed to keep a building at 18 degrees, gives Whangārei Airport 228 cooling degree-days and 1,023 heating degree-days a year. Heating still wins over a full year, so the unit has to do both jobs well.
Humid in every season
NIWA puts the mean 9 am relative humidity at Whangārei Airport at 83% over the year and says it's high in all seasons across Northland. A heat pump on cooling pulls some of that moisture out as water, so the condensate drain matters.
Salt near the shore
BRANZ says homes within 500 m of the coast or harbour, or 100 m of tidal estuaries and sheltered inlets, are in NZS 3604:2011 exposure zone D. An outdoor unit there that works hard all summer needs corrosion protection agreed before installation.
Sizing for cooling when winters are mild
EECA's rule is to size on the cooling capacity at 35 degrees outside if the unit will mainly cool, and on the heating capacity at 7 degrees if it will mainly heat. In a mild-wintered town, a west-facing lounge full of glass can need more cooling than heating, so ask for both figures for that room.
BRANZ says a heat pump's cooling capacity is generally about 10 to 20% lower than its heating capacity, so a unit that comfortably heats a room may struggle to cool it on a hot afternoon. EECA adds that the size and direction of the windows, the insulation and the shading all change the answer.
Don't fix that by buying big. Rinnai NZ says an oversized unit turns off and on frequently, causing wear and tear. If cooling is the main use, BRANZ suggests choosing a unit with a high energy efficiency ratio (EER), which it puts at about 2.5 to 4.0 for typical home heat pumps. Our air conditioning page explains the label's cooling figures.
Where the outdoor unit goes, and the neighbours
BRANZ says heat pumps run most efficiently when the gap between inside and outside temperatures is smallest. For a unit that mostly cools, ask whether its spot gets baked by the afternoon sun. If you add shade, keep it off the unit itself: BRANZ wants at least 500 mm clear in front of the air inlet and outlet.
Summer is when neighbours sleep with their windows open. Whangarei District Council's district plan sets the noise limits, and we haven't sourced its figures, so check with the council if the unit will be close to a boundary. A council sign-off on the install won't protect a noisy unit from enforcement later.
On cooling, the condensate drain runs steadily. BRANZ says the hose should end in a drain or a garden, not on a path.
Questions for a Whangārei cooling quote
- What's the cooling capacity at 35 degrees, and does it cover this room's glass and sun?
- What are its blue star ratings for the Cold zone on the energy label?
- Will the outdoor unit sit in full afternoon sun, and can it be shaded without blocking airflow?
- What corrosion protection is included, and does the brand's warranty need it?
- Where will the condensate drain end up?
What we'd do
Our advice for a Whangārei summer
We'd pick the hottest room you actually want cooled, often the lounge or a west-facing bedroom, and make sure the 35 degree cooling figure covers it, then check the heating side still suits winter evenings. Within reach of the harbour, we'd want corrosion protection written on the quote. And we'd have someone who fits heat pumps for cooling regularly look at the sun on that room before quoting.