Step one: what can the house actually run?
Before anything else, establish the energy source available at the property. This one fact removes most of the options.
Check the meter box for a gas meter, and the kitchen for a gas cooktop or bayonet point. Most established Mandurah suburbs are on the ATCO reticulated natural gas network. Parts of Dawesville, Bouvard and the rural blocks east of the estuary run on bottled LPG instead, which changes the running cost calculation considerably. Plenty of older units and villas in Silver Sands and Greenfields are all-electric with no gas at all.
Then look at the roof. Solar needs a north-facing plane with clear sun and a structure that will carry either collectors alone or collectors plus a tank. If mature trees or a two-storey neighbour shade it, solar is not the answer no matter how good the brochure looks.
Step two: size it for your peak, not your average
The failure mode of an undersized storage tank is cold showers; the failure mode of an oversized one is paying to keep water hot that nobody uses.
- One to two people: 125–160 L electric storage, or a 16 L/min continuous flow unit.
- Three to four people: 250 L electric storage, 135–170 L gas storage, or a 20–26 L/min continuous flow unit.
- Five or more, or a spa bath: 315–400 L electric storage, or a 26–32 L/min continuous flow unit.
Gas storage tanks can be smaller than electric ones for the same household because they reheat much faster. If everyone in your house showers between 6.30 and 7.30am, size up. If usage is spread out, you can size down.
Step three: storage or continuous flow
Storage systems heat water and hold it in an insulated cylinder. They deliver full flow to several outlets at once, keep working during a blackout if they have a standing pilot, and are simple to repair. They also lose heat continuously and can be emptied by a long enough run of showers.
Continuous flow units heat only the water you draw. They never run out, they take up almost no room — useful on the narrow side setbacks in newer Madora Bay and Lakelands lots — and they waste nothing standing by. Against that, they cap flow rate, they need a minimum flow to fire at all, and the electric-only ones draw serious current.
Step four: weigh the four fuel types honestly
Gas is usually cheapest to run on the mains network and reasonable to buy. It needs a gas connection, and external siting or a proper flue. Detail on the gas hot water page.
Electric is cheapest to buy and dearest to run, and in WA you should not assume a cheap overnight tariff exists — confirm that with Synergy. It is the right call for rentals, holiday homes and emergency replacements. See the electric hot water page.
Solar is cheapest to run and dearest to buy, needs the right roof, and always includes a booster for grey weeks. See the solar hot water page.
Heat pump uses roughly a third of the electricity of an element tank, needs no roof work, and suits Mandurah's mild winters particularly well. It has moving parts, makes fan noise, and needs airflow. See the heat pump page.
Step five: check the installed price, not the sticker
The unit price is only part of it. Relocating a system or changing fuel type can add more than the appliance costs. Run the numbers through the cost guide and read the installation page so you know what should be itemised on the quote.
One local note worth building into the decision: anything mounted outdoors within a couple of kilometres of the ocean or the Peel-Harvey Estuary lives in salt-laden air, which shortens the life of casings, frames and heat pump fins. Position and maintenance matter more here than the badge on the front.
Talk it through on (08) 9516 1934, or see where we work on the service area page.
Frequently asked questions
What size hot water system do I need for a family of four?
For a storage system, three to four people typically need around 250 litres of electric storage, or a 135 to 170 litre gas storage tank because gas reheats faster. On continuous flow, a two-bathroom household of four usually wants a 20 or 26 litre per minute unit. Usage timing matters: four back-to-back morning showers is a harder job than the same water spread across a day.
Storage or continuous flow?
Storage heats water in advance and holds it, so it delivers full flow to several outlets at once but loses heat around the clock and can run out. Continuous flow heats only what you draw, so it never runs out and wastes nothing standing by, but flow rate is capped and simultaneous showers can thin it out. Household habits decide it more than house size.
Which hot water system is cheapest to run in Western Australia?
Solar with a well-sized collector array is cheapest to run, followed by a heat pump, then mains gas continuous flow, then gas storage, with electric element storage the most expensive. That ordering flips once you factor in purchase price and how long you plan to stay in the house, which is the trade-off worth doing honestly.
How long should a new hot water system last?
Ten to fifteen years is the realistic expectation for most types in Mandurah, with continuous flow gas units often at the upper end and storage cylinders at the lower. Coastal exposure shortens it. Replacing the sacrificial anode at around the five-year mark is the single cheapest thing you can do to extend a storage tank's life here.