Heat Pump Running Costs in NZ Winter 2026: What You'll Pay Now Power Prices Are Up

Power prices have just gone up — Contact lifted daily charges from 1 May, Genesis raises retail prices an average of 12.8% from 16 May, and Meridian has warned customers to expect up to 7%. So the obvious question, two days into May, is: how much is my heat pump actually going to cost to run this winter, and is it still cheaper than the alternatives?

Short answer: yes, but only if you size it right and run it sensibly. This article walks through the real $/hour and $/winter numbers for the heat pumps NZ homes actually have, recalculates them against the new tariffs, and shows you the four or five behaviours that move the needle on your winter bill — without turning your house into a fridge.

At a Glance

• Heat pumps still win on running cost. Even after the May price hikes, a heat pump delivers heat at roughly 30–35% the cost of a gas heater, plug-in electric, or panel, because for every $1 of electricity it imports, it moves about $3–$3.50 of heat.
• Sizing errors are the biggest hidden cost. Undersized units cycle hard and use more power; oversized units short-cycle and dehumidify badly. Both push your bill up by 15–25%.
• Set point matters more than on/off. Holding 18–20°C is cheaper over a winter than letting the house drop to 12°C and blasting the unit at 26°C to catch up.
• Time-of-use plans only help if you can shift load. Most households on flat-rate plans should not switch unless they also have hot water or EV charging on a timer.

For broader context on what heat pumps cost up front, brand differences, and installation, our complete heat pump guide covers the buying side.

Why the May Price Hikes Change Less Than You'd Think

A 10–13% lift on retail rates sounds painful, and on the bottom line of a $400 monthly bill it is. But for heat pump running costs specifically, the impact is smaller than the headline number suggests, for two reasons.

First, a chunk of the increase is in daily fixed charges — Contact's hike from 1 May is mostly there. Daily charges hit you whether your heat pump runs for one hour a day or twelve, so they don't push your per-hour cost of heating up at all. They do push your overall bill up, but you can't escape them by using less heat.

Second, the per-kWh rate rises that Genesis (12.8% average) and Meridian (up to 7%) are signalling work out to roughly 3–4 cents per unit at most NZ retailers. On a 5 kW heat pump running at a coefficient of performance (COP) of 3.5, that's about an extra 5 cents per hour — meaningful over a full winter, but nowhere near enough to make any other heating method cheaper.

The maths still wildly favour heat pumps. A bar heater pumping out 2 kW of heat draws 2 kWh of electricity per hour. A heat pump producing the same 2 kW of heat draws roughly 0.6 kWh — and that ratio doesn't change because rates went up. Both options got more expensive at the same percentage. The heat pump is still about a third the cost.

What "COP" Actually Means For Your Power Bill

You'll see COP (coefficient of performance) on every heat pump spec sheet. It's the ratio of heat delivered to electricity consumed. A COP of 3.5 means 1 kWh of electricity gets you 3.5 kWh of heat. New NZ-spec wall splits typically rate at COP 4.0–5.0 in lab conditions, but real-world average over a winter is closer to 3.0–3.7 because cold mornings drag efficiency down.

Three things drop your real-world COP:

1. Cold outdoor temperatures. Below about 7°C, efficiency falls. Below 0°C (Otago, Central Plateau, frosty inland Canterbury), it falls a lot. South Island homes should aim for cold-climate-rated units — Fujitsu and Mitsubishi both make units that hold COP 3+ down to around -10°C.
2. Defrost cycles. When frost builds up on the outdoor coil, the unit briefly reverses to melt it, which spikes power use for a few minutes.
3. A dirty filter. The single most expensive thing a homeowner does to their heat pump is leave the indoor filter clogged. A choked filter can drop COP by 10–15%. Clean it monthly in winter — it takes two minutes.

The Real Numbers: Running Cost By Unit Size

Assuming a post-hike average rate of 33c/kWh and a real-world COP of 3.5, here's what you're actually paying per hour of operation:

• 2.5 kW unit (bedroom): 0.71 kWh in, ~24 cents per hour
• 5 kW unit (lounge): 1.43 kWh in, ~47 cents per hour
• 7 kW unit (open-plan): 2.0 kWh in, ~66 cents per hour
• Ducted ~12 kW total capacity: 3.4 kWh in when running, ~$1.10 per hour

Most NZ households with a single-room split run it 4–8 hours a day in winter, so a 5 kW lounge unit costs roughly $2–$3.75 a day, or $60–$115 a month over the worst three months. A South Island home doing the same with a 7 kW unit through a longer, colder winter will land closer to $300–$450 across the season.

A whole-home ducted system is the wildcard. They look expensive per hour, but a well-zoned ducted system actually runs less of the time than people assume — the inertia of a whole house means it doesn't have to fight as hard once it's up to temperature. Ducted homes that zone properly (only conditioning bedrooms at night, only living areas during the day) typically come in at $500–$700 for the winter. Unzoned, run-everything-everywhere ducted setups are where the $1,200+ winter bills come from.

Heat Pump vs Everything Else (Post-Hike Numbers)

For an apples-to-apples comparison, here's what it costs to put 2 kW of useful heat into a room for one hour at 33c/kWh and current NZ gas rates:

The take-home: even after the price rise, a heat pump is the cheapest plug-in heating option in New Zealand by a country mile. The only thing that beats it on running cost is dry, free firewood you cut yourself — and even then you're paying with your weekends. (Solar-fed heat pumping during the day is a separate conversation; we cover the maths of that in solar payback in NZ.)

Sizing: Why Bigger Isn't Cheaper

The most common mistake we see at quoting stage is oversizing, especially in mid-sized lounges. The thinking is "more power = warmer faster = cheaper". It's wrong. An oversized heat pump hits the set-point quickly, then short-cycles — switching on and off repeatedly, which is the least efficient mode of operation and also the worst for the compressor. You pay more, and the unit dies sooner.

Undersizing is the opposite problem: the unit runs flat-out for the whole evening, never quite catching up, drawing maximum power continuously and giving a poor real-world COP.

Rough sizing rule of thumb for an averagely insulated NZ home (post-2008 build standard, double glazing, decent ceiling and underfloor insulation):

• 2.5 kW — bedroom, study, or small office (up to ~25 m²)
• 3.5 kW — generous bedroom or small lounge (25–35 m²)
• 5 kW — typical lounge/dining (35–55 m²)
• 6–7 kW — open-plan kitchen-living (55–75 m²)
• 8 kW+ or ducted — whole-floor open plan, or two adjoining living spaces

Add 20–30% to the recommended capacity if your home is pre-2000, has single glazing, or sits in Otago, Southland, or the Central Plateau. Subtract if you've already done wall insulation and the place holds heat well.

A second, smaller heat pump in a rarely-heated bedroom often beats cranking the main lounge unit harder. Two 2.5 kW units running gently is cheaper than one 5 kW unit running at maximum output, every time.

Settings and Habits That Actually Cut the Bill

Most of what people read online about heat pump running costs is wrong. The four things that genuinely move the needle:

1. Set 18–20°C and leave it. The single biggest myth is "turn it off when you leave the room". For a well-insulated room, holding 19°C all evening uses less power than letting it drop to 14°C and reheating to 22°C every night. The exception is rooms you genuinely don't use for 8+ hours.
2. Use the schedule / timer. Pre-heat the lounge for 20 minutes before you wake up and 30 minutes before you get home — both at lower set-points than you'd manually dial in. Almost every NZ heat pump made in the last decade has a weekly scheduler. Almost no one uses it.
3. Heat mode, not auto mode. Auto mode swings between heat and cool depending on small temperature drift. In a NZ winter, that means it'll briefly switch to cool on a sunny afternoon, then re-heat. Lock it to heat mode May–September.
4. Fan speed on auto, louvres pointed down. Warm air rises. Pointing the louvres at the ceiling is a remarkably effective way to heat your ceiling. Aim them at the floor or the seating area.
5. Clean the filter every month during heavy use. A clean filter alone is worth 10–15% on your winter bill.

Damp houses cost more to heat, full stop, because warming wet air uses more energy than warming dry air, and the moisture gives you that "still cold at 22°C" feeling that drives you to crank the set-point. If your windows fog up most mornings, fixing that — see our winter condensation guide — pays for itself in heating cost alone.

Should You Switch to a Time-of-Use Plan?

Most NZ retailers now offer time-of-use plans with cheaper overnight or off-peak rates and pricier peak-evening rates (typically 5–9pm). They look attractive — until you remember that 5–9pm is exactly when most people run their heat pump.

Switch only if at least one of these is true:

• You also have an electric hot water cylinder you can put on a controlled overnight circuit
• You charge an EV at home and can move charging to overnight
• Your household genuinely doesn't use much heat in the 5–9pm window (shift workers, mostly-empty home in evenings)
• You have solar PV producing most of your daytime heat-pump load

If none of those apply, a flat-rate plan is almost always cheaper for a heavy heat-pump household. Run the numbers with our savings calculator before switching.

Should You Replace an Old (Pre-2015) Heat Pump?

Heat pump efficiency has come a long way. A unit installed in 2010 might have a real-world winter COP of 2.2–2.6. A new equivalent runs at 3.3–3.7. That's roughly a 30–40% reduction in running cost for the same heat output.

Worth replacing this year if:

• It's 12+ years old (compressor reliability falls a cliff at this age)
• It's iced up the outdoor coil more than twice this year
• It can't hold temperature on cold mornings — i.e. you've started using a plug-in heater alongside it
• You're WKH-eligible (the 2026 Warmer Kiwi Homes changes cover up to $3,000 toward a new unit, which often makes a like-for-like replacement effectively free)

Probably not worth replacing if it's under 8 years old, holds set-point on cold mornings, and the filter and coils are clean. Service it instead — a $200 service every two years gets you most of the way to a new unit's performance.

What to Do Next

If you're already running a heat pump, the cheapest two changes you can make for winter 2026 are: clean the filter today, and check that you're holding 18–20°C continuously rather than blasting and cooling. That alone is worth 10–20% on your winter bill, before you spend a cent.

If you're sizing or replacing a unit, get quotes from verified heat pump installers in your area — and check whether you're eligible for a Warmer Kiwi Homes subsidy before you commit. A $3,000 grant turns a $4,500 install into a $1,500 install, which changes every payback calculation.

Power got more expensive on 1 May. The heat pump in the corner is still the cheapest weapon you've got against a NZ winter — provided you point it the right way.