Quick answer
In the heat pump vs gas hot water choice, heat pumps cost more upfront but are cheap to run, especially with rooftop solar, and may attract rebates. Gas systems, usually continuous flow, are compact and give endless hot water but carry gas supply and usage costs. In SA, most replacement water heaters must be a low-emission type.
Heat pump vs gas hot water is the big decision for many Adelaide households when an old system starts leaking or running cold. Both can supply a family reliably. They differ in upfront cost, running cost, noise, where they can go, and how well they fit with rooftop solar and future plans to move off gas.
This guide compares the two honestly, explains South Australia’s rules for replacement water heaters, covers rebates and discounts, and looks at how heat pumps compare with solar hot water. It doesn’t list prices, which vary a lot by model and installation. A licensed plumber will quote your job.
How do heat pump and gas hot water systems work?
A heat pump water heater works like an air-conditioner in reverse. It uses a refrigeration cycle to pull heat from the surrounding air and transfer it into a storage tank. According to energy.gov.au, heat pumps are highly efficient and use around 30% of the energy of a conventional electric hot water system.
Gas water heaters burn natural gas or LPG to heat water. Most new gas systems are continuous flow (instantaneous) units, which heat water only as you use it. Gas storage tanks are also available. Energy.gov.au notes gas units are usually installed outdoors because of venting requirements.
Heat pump vs gas hot water: how do they compare?
| Factor | Heat pump | Gas (continuous flow) |
|---|---|---|
| Upfront cost | Higher to buy and install | Usually lower to buy; installation varies |
| Running cost | Low, especially with solar power | Medium to high, plus gas supply charges |
| Hot water supply | Stored tank, can run out if overused | Continuous while gas and water flow |
| Space needed | Floor space for a tank and compressor outside | Compact wall-mounted unit |
| Noise | Compressor and fan noise, like an air-con unit | Quiet, with some fan and burner noise |
| Cold weather | Some models aren’t designed for regular sub-5 °C winters | Not affected by air temperature |
| Works with rooftop solar | Yes, can be timed to run on daytime solar | No direct benefit |
| Rebates | May be eligible for STCs and retailer discounts | High-efficiency models may qualify for some offers |
| Emissions | Low, lower again on renewable power | Ongoing gas combustion |
What does a heat pump cost to run compared with gas?
A heat pump is usually the cheaper system to run, but the gap depends on your situation. Energy.gov.au describes heat pumps as expensive to purchase and install but cheap to run, and gas systems as having medium-to-high purchase, installation and running costs.
Things that tip the balance:
- Rooftop solar. If you have solar panels, setting the heat pump to run in the middle of the day uses power you’d otherwise export for a low feed-in rate.
- Your gas connection. If hot water is your last gas appliance, switching to a heat pump may let you close the gas account and stop paying the daily supply charge.
- Household size and habits. Large families using lots of hot water in the evening need a correctly sized tank.
- Tariffs. Electricity and gas prices vary by retailer and plan.
What are SA’s rules for replacing a water heater?
South Australia has energy-efficiency requirements for new and replacement water heaters. According to the SA Government, for most homes that means installing a low-emission water heater, such as high-efficiency gas, solar or an electric heat pump, along with water-efficient shower heads or flow restrictors.
The type of system you can install in an established home depends partly on whether the home is connected to mains gas. The SA Government website has a tool to check which water heater your home can have, and a licensed plumber will know the current requirements.
Working water heaters don’t have to be replaced just because the rules exist. The requirements apply when you install or replace one.
Hot water safety rules also apply. In South Australia, heated water at outlets used mainly for personal hygiene, such as showers, baths and basins, must not be delivered at more than 50 °C. Your plumber will fit a tempering valve or similar device where required. Our guide to pressure relief and tempering valves explains how these work.
Is there a heat pump hot water rebate in SA?
There are two main sources of help, and neither is a simple fixed cash rebate.
Small-scale technology certificates (STCs). Energy.gov.au explains that solar and heat pump hot water systems could be eligible for STCs, which can be traded for cash or a discount on the purchase price. In practice, installers usually apply the value as a discount on your quote.
Retailer Energy Productivity Scheme (REPS). The SA Government explains that energy retailers taking part in REPS may offer free or discounted energy upgrades, including help to save on water heating costs. You don’t have to be a customer of the retailer to access their offers, and priority group households may be eligible for further discounts.
Ask any installer to show STC and REPS discounts as separate lines on the quote, so you can see the full price before and after.
Heat pump vs solar hot water: which is better?
Both are low-emission options that suit Adelaide’s sunny climate. The choice usually comes down to your roof and your setup.
- Solar hot water uses collectors on the roof to heat water, usually with a gas or electric booster for cloudy days. It needs a suitable, unshaded, well-oriented roof area.
- A heat pump sits on the ground, works in most weather and doesn’t need roof space. It pairs neatly with rooftop solar panels you already have.
If your roof is already covered in solar panels, or it faces the wrong way, a heat pump is often the simpler choice.
Where does a heat pump work best?
Placement matters more with heat pumps than with gas. Energy.gov.au notes the compressor can be noisy, similar to an air-conditioning unit, and that not all models are designed for cold locations where it regularly drops below 5 °C in winter.
For Adelaide Hills homes, ask whether the model you’re considering is suited to colder winters. On the plains, the main consideration is noise: keep the unit away from bedroom windows and boundary fences near neighbours’ living areas, and time it to run during the day.
What should I ask before choosing a system?
Asking a few questions up front makes it much easier to compare a heat pump and a gas system fairly.
- What size tank or flow rate suits my household?
- Which options comply with SA’s requirements for my home?
- What rebates or retailer discounts apply, and are they shown on the quote?
- Where will the unit go, and how much noise should I expect?
- Is the model suited to colder Hills winters, if relevant?
- What’s included: removal of the old unit, valves, electrical or gas work?
When should you call a licensed plumber?
Talk to a licensed plumber before your current system fails, if you can. Replacing on your own timeline gives you time to compare system types and check rebates.
Call sooner if you notice:
- water pooling under the tank or a rusty tank base
- the relief valve dripping constantly
- lukewarm water or running out faster than usual
- a gas unit that won’t ignite or shows a fault code
- a gas smell (leave the house and call 1800 427 532 or 000)
Installing hot water systems is licensed plumbing work, and gas connections must be done by a licensed gas fitter. See our heat pump hot water and hot water systems pages, the Adelaide plumber hub, or our guide to hot water system replacement cost.
Getting it sorted
If you’re deciding between heat pump vs gas hot water, send one enquiry through our contact form or call 08 6800 6079. We pass it to one local plumber, who calls back within 24–48 hours to talk about your household, your current setup and the options that comply, then quotes before any work starts. Check the manufacturer’s warranty terms on any system you’re offered.
Sources
Stock photo, for illustration only. This guide is general information for Adelaide homeowners, not professional advice. In South Australia, electrical, plumbing and gas work must be carried out by an appropriately licensed tradesperson, and rules change, so check current requirements with the relevant authority.
