A like-for-like hot water system replacement in Perth typically costs $3,000–$3,500. Switching to a different type, gas to heat pump, or storage to continuous flow, usually runs $4,500–$7,000, because the gas, power and pipework have to change along with the unit.
Below are four real jobs, priced at our current plumbing rates, showing exactly what moves the number.
Need a new hot water system quote? We offer free onsite quotes with no call-out fees! Call 1300 634 581 to book one of our local plumbers today.
Why the Type You Choose Matters More Than the Brand
When a hot water system reaches the end of its life, the first decision isn’t the brand, it’s the type: storage tank, continuous flow, or heat pump. That choice, and whether you stick with what you’ve got or switch, drives the price more than anything else.
The general rule: a like-for-like swap is the cheapest path, because the gas, water and power are already where the new unit needs them. Switching types means changing the supporting infrastructure, gas lines, power points, pipework, and that’s where the price moves. Heat pumps add one more wrinkle in your favour: government rebates that take real money off.
Four Perth Hot Water System Replacement Jobs and What They Cost
Job |
Type of change |
Cost (inc. GST) |
What drove the price |
|---|---|---|---|
| Seville Grove | Continuous flow → continuous flow (like-for-like) | $3,161.56 | No new gas run or power work needed |
| Mount Claremont | Gas storage → heat pump | $4,639.69 | New pipework, valves and power connection; ~$800 rebate applied |
| East Cannington | Solar (with gas booster) → heat pump | $5,225.88 | Roof plumbing rerouted plus new power connection; ~$800 rebate applied |
| Swan View | Storage → continuous flow | $7,068.60 | Gas line upgraded to 32mm to support on-demand heating |
Continuous flow hot water system swap (Seville Grove)
What was required
The existing Rinnai 20L continuous flow unit had failed. The heat exchanger inside was leaking, and the water was getting into the control board and killing that too. Once a heat exchanger goes, replacement beats repair on cost every time.
What it cost
$3,161.56
Why did it cost $3,161.56?
This is the like-for-like path. One of our licensed gasfitters tested the gas supply first to confirm there were no existing leaks, decommissioned the old unit, and installed a new Rinnai 20L continuous flow in its place, secured to the wall with a new valve kit and the pipework modified to suit. Commissioned, tested for leaks, correct operating pressure confirmed. Because the new unit went where the old one was, there was no new gas run or power work, and the price stays at the lower end of the typical range for a hot water replacement job.
Gas storage tank system to a heat pump system (Mount Claremont)
What was required
The customer was done with their old gas storage unit and wanted to switch to an iStore 270L heat pump, which runs on a fraction of the energy.
What it cost
$4,639.69
Why did it cost $4,639.69?
Switching from gas to a heat pump is more than a swap. We drained and decommissioned the old gas unit and capped off the gas, reconfigured the pipework to suit the heat pump, and fitted all new valves including a temperature mixing valve. The price also includes the electrician to run and connect power to the new unit, so one price covered the whole system change-over. A government rebate of around $800 applied to this unit, and we lodged the paperwork, so the customer’s real cost came in well under the final invoice figure.
Corroded solar hot water system replaced with a heat pump system (East Cannington)
What was required
The old solar hot water system with its gas booster had corroded and had stopped working completely. The customer chose an iStore 270L heat pump as the replacement, giving them a modern, efficient solution without the need for a gas booster.
What it cost
$5,225.88
Why did it cost $5,225.88?
A solar hot water system to heat pump system conversion is the biggest change-over of the lot. The existing hot and cold-water lines ran into the roof space to service the old solar unit, so we located them and installed new pipework down to the heat pump’s new location.
The old gas booster was drained and the gas supply capped off. We also installed new valves and a temperature mixing valve, while an electrician ran the power supply to the new heat pump. We then lodged the rebate paperwork on the customer’s behalf, with around $800 expected back.
The additional cost compared with the Mount Claremont job was mostly due to the roof plumbing and the need to reroute supply lines that had originally been installed for a completely different system located on the roof.
Storage tank hot water system to continuous flow hot water system (Swan View)
What was required
A storage tank hot water unit had failed and was leaking. We quoted both paths: a like-for-like storage swap, or a switch to a Thermann 26L continuous flow. The customer chose to make the switch, opting for a more compact system that provides hot water on demand without the need to store and continually reheat a tank of water.
What it cost
$7,068.60
Why did it cost $7,068.60?
This job is a good example of what “switching types” can actually involve. A continuous-flow hot water system heats water on demand, so it requires a significantly higher gas flow than a storage system that heats water gradually throughout the day.
In this case, that meant upgrading the gas supply with a new 32mm gas line from the first branch to ensure the new unit could operate correctly. We also installed a new power point, decommissioned and removed the old storage unit, and installed the new Thermann continuous-flow system.
Without the gas upgrade, the new unit would not have been able to perform as intended. It’s the difference between simply fitting a new hot water system and doing the job properly, which is why we identify and price these requirements upfront rather than discovering them halfway through the installation.
Looking to install a new hot water system?
Looking to install a new hot water system? Call Swans Professional Plumbing for expert advice and a properly quoted installation. We’ll help you choose the right system for your home and make sure everything is installed correctly from the start.
FAQ
A like-for-like swap, like the Seville Grove job above, is typically a same-day job. A full type change, gas to heat pump or storage to continuous flow, usually still fits in a day but can run longer where roof plumbing or a gas line upgrade is involved, as in the East Cannington and Swan View jobs.
Not always. We check this before quoting a replacement unit, sometimes it's a failed valve or part, not the whole unit, and repair is the cheaper honest answer.
No. In Western Australia, gas and electrical work must be carried out by appropriately licensed tradespeople. A licensed gasfitter is required for gas connections, while electrical work must be completed by licensed electrician. We coordinate these trades as part of the installation, so the required work is included in the upfront price rather than appearing as an unexpected extra.
Using unlicensed tradespeople can also result in an unsafe or non-compliant installation, potentially creating gas leaks, carbon monoxide exposure, electrical hazards or fire risks, as well as causing issues with insurance and liability if something goes wrong. That’s why we make sure the required licensed work is handled properly from the outset.
Continuous-flow units require a significantly greater gas supply than traditional storage tanks. In this case, upgrading the gas line to 32mm was essential to provide the new unit with the gas flow it needed to perform as designed. It wasn’t an optional extra, it was a necessary part of installing the system correctly.
