Hot Water Heat Pump vs Gas Hot Water: NZ Comparison (2026)

A hot water heat pump works on the same principle as a refrigerator, but in reverse. Instead of extracting heat from inside a box and pumping it out, it extracts heat from the surrounding air and uses it to heat the water in a hot water cylinder.

The system uses a compressor and a refrigerant (CO2, R290, or R134a depending on the model) to absorb heat energy from ambient air, even on cold days. That heat is concentrated by the compressor and transferred to the water in the cylinder. Because the system is moving heat rather than generating it, it uses far less electricity than a conventional electric element.

The key metric is the Coefficient of Performance (COP). A COP of 3.5 means that for every 1kW of electricity consumed, the heat pump delivers 3.5kW of heat into the water. That is why hot water heat pumps are typically 3-4 times more efficient than the electric cylinders most New Zealand homes still run, and why they undercut gas on running cost as well.

Residential systems come as either integrated units (compressor and cylinder in one) or split systems (a separate outdoor compressor connected to the cylinder by refrigerant lines). Split systems tend to be quieter and more efficient; integrated units are simpler to install.

Gas hot water systems burn natural gas or LPG to heat water directly. There are two main types:

Gas storage systems heat water in an insulated tank and keep it hot around the clock. A pilot light or electronic ignition fires the burner when the water temperature drops below a set point. These systems have standing heat losses because the tank constantly radiates stored heat.

Gas instantaneous (continuous flow) systems heat water on demand as it flows through the unit. They avoid standby losses but draw heavily during peak demand and can struggle to supply multiple outlets at once.

Both types need a gas supply and a flue, and installation must comply with AS/NZS 5601 gas installation standards, carried out by a licensed gasfitter.

The crucial New Zealand context: reticulated (piped) natural gas exists only in the North Island, serving roughly 270,000 homes. South Island homes that use gas rely on bottled LPG. So the gas-versus-heat-pump question is mostly a North Island question; in the South Island the comparison is usually electric cylinder versus hot water heat pump.

Running costs are where hot water heat pumps win decisively. Here is an indicative comparison for a typical 3-4 person household:

Assumptions: electricity at about 35c/kWh (typical NZ residential range 33-38c), 150-200L of hot water per day. Indicative only; your usage and plan will differ.

We deliberately do not quote a single annual dollar figure for gas. Gas pricing combines a variable rate with daily fixed charges, both of which are rising as the gas supply crunch bites, and plans vary widely. What is clear from the supply data is the direction: gas running costs are heading up, while heat pump running costs are tied to electricity, where you can shop between retailers.

The savings improve further if you have solar panels. Running the heat pump in the middle of the day on your own solar generation costs you only the export buyback you forgo, currently around 7-12c/kWh, instead of the full retail rate. Gas systems cannot use rooftop solar at all.

Upfront cost is the one area where gas has traditionally been cheaper, and unlike Australia, New Zealand has no rebate scheme to close the gap. The honest picture (GST inclusive, indicative June 2026):

• Hot water heat pump replacement: $6,000-9,000 for a typical straightforward job. Entry-level installed bundles start from about $6,400. Complex jobs and relocations run $9,000-13,000.
• Like-for-like gas replacement: usually cheaper upfront, but it recommits you to gas bills and gas servicing for the next decade on a network that is shrinking.

The real comparison is total cost of ownership. A hot water heat pump that saves you $900-1,100 a year against an electric cylinder, or a meaningful (and growing) margin against gas, recovers its installed price over its service life, then keeps saving.

On financing: there is no NZ government rebate for hot water heat pumps, but the major banks offer green home loan top-ups: ANZ, ASB and BNZ at around 1% p.a. fixed for 3 years (up to $80,000), and Westpac at 0% for up to $50,000 over 5 years. See our NZ financing guide for the details and the catches.

New Zealand has no legislated gas ban, but the supply picture has deteriorated sharply, and it is the single most important fact for anyone weighing up a new gas hot water system.

• Proven plus probable gas reserves fell 27% in a single year, from about 1,300 PJ in 2023 to 948 PJ in 2024, a 20-year low.
• Annual production was 155 PJ in 2023, dropped to 125 PJ in 2024, and is expected to fall to around 85 PJ in 2026, declining faster than forecast.
• The result: rising household gas prices, retailers rebalancing away from gas, and officials and industry expecting consumer switching to accelerate through the late 2020s.

A new gas hot water system installed today is a 10-15 year commitment to fuel from a shrinking pool, with fixed network charges spread across fewer and fewer connections. That is the structural risk a hot water heat pump avoids. Read the full story in our NZ gas crunch guide.

Hot water heat pumps typically last 10-15 years. The main maintenance is keeping the evaporator coil clear of leaves and debris and having the cylinder anode checked every few years (stainless cylinders skip the anode). There are no pilot lights or combustion parts to service.

Gas storage systems need periodic servicing of the burner, thermocouple and gas valve, plus anode checks. Pilot light failures are a common call-out.

Gas instantaneous systems can last longer but want regular servicing, including descaling in hard water areas.

Noise is worth planning for with a heat pump. Split systems are quieter than integrated units, and placement matters: keep the unit away from bedroom windows and boundaries, and check your district plan noise limits. Gas storage systems are essentially silent.

Space: heat pumps need clearance around the unit for airflow (roughly 300mm each side and more above). Gas systems need flue clearances and setbacks from windows and boundaries.

Whoever does the work: cylinder and pipework changes are a job for a certifying plumber, and any new circuit or wiring must be done by an EWRB-registered electrician.

For most New Zealand households, a hot water heat pump is the better long-term choice. How to think about it:

Strong candidates for a hot water heat pump:

• Households with solar panels (cheap daytime hot water)
• North Island homes on reticulated gas whose system is near end of life (get ahead of rising gas bills)
• Anyone replacing an ageing electric hot water cylinder (65-75% energy saving on hot water)
• Households focused on cutting energy bills for the long haul
• Properties with outdoor space for the unit

Situations where gas may still make sense for now:

• A recent, working gas system: run it to end of life rather than scrapping it early
• Homes with no workable location for a heat pump unit
• Apartment buildings with centralised gas hot water (a body corporate decision)

If you are on gas in the North Island, the question is less whether the economics will tilt further against gas and more when. Replacing proactively at end of life, rather than in an emergency, lets you choose the system, the installer and the timing. Get free quotes from local installers to see real numbers for your home.