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Heat Pump vs Gas Hot Water in Melbourne: Which One Is Right for Your Home?
Heat Pump vs Gas Hot Water in Melbourne: Which One Is Right for Your Home? — a Prime Plumbing & Gasfitting plain-English guide to heat pump vs gas hot water melbourne for Melbourne homeowners. Below we cover what works, what doesn't, and when to call a licensed plumber.
Quick answer: For most Melbourne homes replacing an end-of-life gas hot water unit in 2026, a heat pump is now usually the better choice on running cost — typically half the energy cost of gas — once the Victorian Energy Upgrades (VEU) rebate is applied. Upfront cost is higher than a like-for-like gas swap, but the VEU rebate plus federal STCs typically bring net install cost close to gas. The main reasons to stick with gas are: limited outdoor space for a heat pump, very high hot water demand (large families, multiple bathrooms drawing simultaneously), or a recently-installed gas unit with years of life left. Both technologies are reliable when well-installed and properly serviced. Heat pump install does NOT require a gasfitter; gas install does — your installer must hold the appropriate licence either way.
Why this comparison matters in Melbourne right now
Melbourne households are weighing up hot water options in a different context than five years ago. Three things changed:
- Victorian gas prices have risen substantially, narrowing the running-cost gap that used to favour gas
- Heat pump efficiency has improved — modern units deliver 3-4 kWh of heat per 1 kWh of electricity input
- VEU and federal STC rebates make heat pumps significantly cheaper to install than they were
Plus the longer-term policy direction: Victoria has stopped requiring new homes to connect to gas, and several councils have moved further on gas restrictions. Existing gas connections are still completely legal, but the trajectory is clear.
That said, "trajectory" doesn't replace a hot water unit on a Tuesday morning when yours has stopped working. The question is what's the right replacement for your specific home, not what the policy direction says.
The Tuesday-morning question — replace like-for-like or switch?
When your existing unit fails, the constraint is rarely "what is the optimal long-term choice" — it is "how do we get hot water back today, within budget, with the household running". Like-for-like (gas → gas, electric → electric) is usually 1-2 days install. Switching technology (gas → heat pump) involves new wiring, the old gas service decommissioning, and rebate paperwork — typically 2-4 weeks elapsed time. For emergency replacements we lean like-for-like; for planned end-of-life we walk through both. See our hot water system installations and repairs page.
How each technology works
Gas storage and gas instantaneous
A gas storage hot water unit burns gas to heat water in an insulated tank, holds it at temperature (typically 60-65 °C in the tank), and supplies on demand. The tank cycles on and off as the water cools, which means there's a small standing energy loss even when nobody's using hot water.
A gas instantaneous (continuous-flow) unit doesn't store water. It heats water as it flows through, on demand. No standing loss, but a higher peak gas burn rate.
Both rely on a flue to vent combustion products outside. Both require an annual or 2-yearly gasfitter service to stay safe (CO testing on flued units, leak testing on connections). Both are installed by a Type A Gasfitter.
Heat pump
A heat pump hot water unit works like a reverse air conditioner. It pulls heat from the outside air and uses it to heat water in an insulated tank. The compressor uses electricity, but most of the heat in the water came from the ambient air outside — which is why heat pumps are 3-4× more efficient than direct electric resistance heating.
Modern heat pumps work down to about -5 °C ambient. Melbourne winters are mild compared to alpine areas, so a heat pump in Melbourne sees efficient operation most days of the year, with a small efficiency drop on the coldest nights.
A heat pump install doesn't need a gasfitter — it's an electrical and plumbing install. There's no flue, no gas connection.
Running cost comparison
This is the headline number most homeowners care about. The honest answer is: it depends on your hot water usage, your gas tariff, your electricity tariff, and whether you have solar.
For a typical Melbourne household using around 200 L/day of hot water (mid-sized family), the rough annual running cost in 2026 is:
| Technology | Annual energy cost (no solar) | Annual energy cost (with solar) |
|---|---|---|
| Gas storage | $700-$1,100 | $700-$1,100 (same) |
| Gas instantaneous | $600-$1,000 | $600-$1,000 (same) |
| Heat pump | $250-$500 | $50-$200 |
These are indicative ranges — your actual bill depends on hot water usage, tariff, and whether your heat pump runs during solar production hours.
The big number is the heat-pump-with-solar bottom row. If you've got solar PV and a heat pump scheduled to run during the day, the marginal cost of hot water can drop close to zero. That's the scenario where a heat pump pays back fastest.
For homes without solar, the gap is narrower but still favours heat pumps on running cost — typically by $300-$500/year.
Upfront cost and rebates
Gas storage replacement (like-for-like)
Typically $1,800-$3,500 supply and fit for a like-for-like replacement gas storage unit, depending on capacity and access.
Gas instantaneous
Typically $2,200-$3,800 supply and fit, depending on capacity and existing pipework.
Heat pump
The unit cost is higher — typically $4,000-$6,000 for the unit alone, $5,500-$8,500 supply and fit before rebates. After rebates, the net install cost typically lands at:
- Victorian Energy Upgrades (VEU) rebate: typically $1,000-$2,800 off, depending on unit
- Federal STCs (Small-scale Technology Certificates): typically $300-$1,200 depending on zone and unit
- Net cost after both rebates: typically $2,800-$5,500 supply and fit
So the upfront cost gap between gas and heat pump, post-rebate, is often $500-$2,000 — not as wide as the headline numbers suggest.
The VEU and STC rebates are administered by the installer, not claimed by you separately. We'll calculate them at quote time and apply them directly.
When heat pump is the better choice
- End-of-life gas unit — when you're replacing anyway, heat pump payback timing improves
- Solar PV already installed — best-case running cost scenario
- Moderate household size — 2-4 people, typical hot water demand
- Outdoor space available for the unit (typically 1m × 2m clear)
- Long-term ownership — you'll capture the running-cost savings over 8-12 years
- Looking ahead on gas — even if you're not philosophically anti-gas, the price and connection trajectory matters for resale
What to expect on installation day
Gas like-for-like replacement
- Old unit removed (usually 1-2 hours)
- New unit installed in the same location
- Gas connection pressure-tested
- Tempering valve fitted at outlet (mandatory under AS/NZS 3500.4)
- Hot water tested at outlet
- Compliance Certificate lodged with the VBA within 5 business days
- Total job: typically 4-6 hours
Heat pump install
- Old unit removed
- Concrete slab or wall mount prepared if required (sometimes a separate visit)
- Heat pump tank and compressor positioned
- Plumbing connections, tempering valve fitted
- Electrical connection (a sparky if a new circuit is needed; we coordinate)
- Initial fill, leak test, electrical test, commissioning
- Compliance Certificate lodged with the VBA
- VEU + STC paperwork lodged
- Total job: typically 1 full day, sometimes split over 2 days for slab prep
For both, you can expect to be without hot water for the duration of the changeover (usually 4-8 hours).
Service area
Prime Plumbing & Gasfitting installs heat pumps and gas hot water across Melbourne's eastern, south-eastern, inner-east and bayside suburbs. See all suburbs we service →
Book a hot water replacement quote
Call 0475 407 670 or send through the contact form. Tell us your existing unit type, household size, and whether you have solar — we'll quote both options where they're both viable.
- BPC #103414 — Plumbing Industry Commission licensed
- Type A Gasfitter — registered with Energy Safe Victoria
- VEU and STC rebates — calculated and applied at quote time
- 4.8 stars on Google
Reliability and service life
Both technologies are reliable when well-installed and well-serviced.
Gas hot water service life
- Gas storage: typically 10-15 years
- Gas instantaneous: typically 12-18 years (continuous-flow units last slightly longer because there's no tank to corrode)
Common failure modes: tank corrosion (storage), heat exchanger fouling, regulator wear, igniter failure, sediment-blocked inlet.
Heat pump service life
- Heat pump: typically 10-15 years for the unit overall, with the compressor often the limiting component
Common failure modes: compressor wear, refrigerant leaks, electronic control board failure, fan motor wear (outdoor units exposed to weather).
Heat pumps have more electronics than gas units, so they're slightly more sensitive to surge/lightning damage and more dependent on a stable power supply. In a Melbourne suburban context, this isn't a major consideration.
When gas is still the right choice
We don't push every customer to heat pump — there are real cases where gas is better:
- Limited outdoor space for the heat pump (the unit needs clearance for airflow; it can't be boxed in)
- No suitable mounting surface outside (no slab, no concrete pad, no wall space)
- Very high simultaneous hot water demand — large families, multiple bathrooms drawing at once. A 270 L heat pump can struggle to keep up where a 26 L/min gas instantaneous handles it without breaking a sweat.
- Recently-installed gas unit with 5+ years of life left — replacing isn't financially sensible
- Renters — landlord may not approve heat pump install
- Specific architectural constraints — heritage façades, body corp restrictions on outdoor equipment
If gas is the right call for your home, our hot water systems service covers like-for-like gas replacements. The work is done by a Type A Gasfitter with Compliance Certificate.
When to call a licensed plumber
The Victorian Building Authority maintains a plumbing licence search so you can verify your installer.
Frequently asked questions
Modern heat pump compressors run at around 45-55 dB(A) at the outdoor unit — about the same as a household fridge or quiet conversation. They're not silent, but they're far quieter than older split-system air conditioners. Mounting on a vibration-isolating pad and away from bedroom windows minimises noise transfer. If your neighbour is sensitive to noise, check the unit's dB rating before specifying.
Marginal increase — for a typical household, the heat pump adds around $250-$500/year to electricity (no solar) but eliminates $700-$1,100/year of gas. Net-net, you're saving. With solar, the increase is much smaller because the heat pump can run during daytime solar production.
The VEU scheme is reviewed periodically and the rebate amounts can shift. As of 2026 the rebate is significant; we'll always quote with the current rebate applied so you know the actual net-of-rebate price. If the scheme changes between quote and install, we'll requote.
Yes — many homes keep gas for cooking and heating while moving hot water to heat pump. Gas connection charges still apply on your gas bill, but your overall energy cost usually drops. If you also move cooking and heating off gas at some future point, you can disconnect gas entirely.
Yes. Modern heat pumps designed for Australian conditions work well down to about -5 °C ambient — colder than Melbourne sees on most winter nights. There's a small efficiency drop on the coldest nights, but the unit doesn't stop working. Cold-climate-rated units (made for Tasmania and alpine NSW) are available if you want extra margin, but a standard unit is sufficient for Melbourne metro.
Solar thermal hot water (rooftop panels with a tank below) was popular in the 2000s but has been largely overtaken by PV + heat pump for most installs. PV solar is cheaper per kWh than solar thermal, and a heat pump is more efficient than electric boost. Existing solar thermal systems are still good when working — but most replacements today go to heat pump.
A 270 L heat pump typically supplies 2-4 person household hot water for a typical day's use, with full recovery overnight. For larger households (5+ people, multiple bathrooms) a 315 L or larger unit, or a gas instantaneous, is usually a better fit. We'll size the unit at quote time based on your actual demand.
Before You Book
A quick checklist to share with your plumber when you book:
- When did the issue start?
- Is it isolated to one fixture or multiple areas?
- Are there any visible leaks, smells or unusual sounds?
- Have you turned off the relevant isolation valve?
- Hot water systems Melbourne — new and replacement HWS installs (gas, electric, heat pump)
- Hot water replacement Melbourne — like-for-like and upgrade replacements
- Gas fitter Melbourne — for gas-side service and install work
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