A young couple in Leppington rang me about the solar hot water system on the house they had just bought. Two flat panels on the north face, a 300 litre tank in the garage, and a booster switch on the laundry wall that nobody had explained. They had been paying full electricity rates to heat water in midsummer because the booster had been left on for years. A timer on the booster circuit, fitted by a sparky, fixed it. That is the story of solar hot water across South West Sydney: good technology, installed cheaply, set up wrong, and blamed for it. Here is how it works, what moves the price, and when I'd steer you to a heat pump instead. If the shower is cold right now, we are a hot water plumber, no call-out fee, across Liverpool, Campbelltown and Camden.
A solar hot water system uses collectors on the roof to heat a storage tank, with an electric or gas booster for cloudy days and winter. Flat plate collectors suit most South West Sydney roofs; evacuated tubes cost more but handle frost and overcast weather better. Federal STCs come off the price and the NSW incentive covers electric boosted systems. For most houses in 2026 a heat pump is the simpler buy; solar wins for big households with a clear north facing roof.
How does a solar hot water system work?
Collectors on the roof absorb heat from the sun and pass it into a storage tank. A booster, either an electric element or a gas unit, makes up the difference on grey days and through winter. The panels do the heavy lifting from about September to April, and the booster carries June and July.
There are two layouts. A close coupled system has the tank on the roof above the collectors. Hot water rises into it on its own (a thermosiphon), so there is no pump and little to go wrong except the tank. The catch is weight: a full 300 litre roof tank comes in at around 420 kilograms with the frame, and it wants solid framing spread across several rafters. A split system puts the collectors on the roof and the tank on the ground, with a small pump and a controller that sends water up whenever the panels are hotter than the tank. It costs more and the pump wears, but the weight stays off the roof and the tank is where I can get at it.
Evacuated tube vs flat plate collectors
A flat plate collector is a glazed, insulated box with a dark absorber plate and copper tubes through it. Simple, cheaper, and on a north facing Sydney roof it makes plenty of hot water for eight months of the year. Evacuated tube collectors are rows of glass tubes, each with a vacuum between its double walls, like a thermos. The vacuum stops heat escaping, so they hold their output on cold, overcast days, and each tube carries a sealed heat pipe rather than your water, so nothing in it can freeze. They cost more, weigh less, and if one tube breaks you replace the tube, not the collector.
Which one? Around Liverpool and Fairfield a good flat plate system is fine. Out past Narellan towards Camden, where the paddocks are white most July mornings, I lean towards evacuated tubes or a frost rated flat plate system.
Solar hot water boosters: electric or gas
An electric booster is an element inside the tank, like a standard electric unit. A gas booster is a continuous flow gas unit fitted after the tank, and its burner only fires if the water leaving the tank is below the set temperature. Gas boosting never heats water the sun has already heated, which makes it efficient, but it needs a gas line, costs more up front, and the NSW incentive is built around electric boosted systems; gas boosted solar only qualifies where it replaces an existing gas heater.
The setup matters more than the fuel. A booster left on around the clock heats the tank at dawn, and the sun arrives to find the job done. Put the electric booster on a timer for late evening, or on the off-peak controlled load tariff (an electrician wires either), so the panels get first go. A manual boost switch is for the third grey day in a row, not every morning. Plenty of the "my solar doesn't work" calls I get in Oran Park are a booster wired to run all day.
Roof, frost and where everything goes
Collectors want to face north, or close to it, clear of trees and the neighbour's second storey. North east or north west loses a little; due west loses more but still works with a bigger collector. On a close coupled system I check the framing before I quote, because the whole weight sits in one spot.
Frost is the thing people forget. A flat plate collector full of water on a Camden roof at minus 3°C can split a riser tube. The fixes are a frost rated collector, a closed loop running glycol through the panels and a heat exchanger instead of your drinking water, or evacuated tubes, which keep the water up in the insulated manifold. The tank also needs a solar rated tempering valve, because a solar tank on a February afternoon can pass 80°C and NSW rules cap bathroom hot water at 50°C. More on that in tempering valves and thermostatic mixing valves.
Solar hot water system cost, STCs and the NSW incentive
There is no honest single figure for a solar hot water system price, so I quote it on inspection. What moves it: flat plate or evacuated tube, close coupled or split, electric or gas booster, a single or two storey roof, any roof strengthening, the frost protection and the solar rated tempering valve. As a rule the finished job costs more than a heat pump, which Sydney 2026 price guides put at $3,450 to $6,900 before rebates, and a lot more than a plain electric tank; the wider picture is in hot water system installation cost in Sydney.
Two rebates help. Federal STCs (small-scale technology certificates) apply to solar water heaters as well as heat pumps: the system has to be on the Clean Energy Regulator's register, under 700 litres, and installed by a licensed plumber, and the installer claims the certificates and takes them off the price up front. The number depends on the model and your postcode, and it shrinks every year as the scheme winds down to 2030. The NSW hot water upgrade incentive also covers electric boosted solar replacing an existing electric or gas water heater, through an accredited provider with a minimum co-payment; gas boosted solar is only in the scheme where it replaces an existing gas heater. Check the official page; the rules move.
| Item | Solar hot water | Heat pump | Electric storage |
|---|---|---|---|
| Installed cost (Sydney 2026 price guides) | Quoted on inspection, usually above a heat pump | $3,450 to $6,900 before rebates | $920 to $2,875 |
| Rebates | STCs; NSW incentive, mainly for electric boosted | STCs plus NSW incentive, roughly $900 to $1,350 off | None |
| Needs a roof | Yes: north facing, unshaded, strong | No | No |
| Noise | Silent | Fan and compressor | Silent |
| Winter | Booster does most of the work | Works to at least minus 5°C | No change |
| Wearing parts | Tank, booster, pump, tempering valve | Compressor, fan, controls | Element, thermostat |
Solar vs heat pump hot water: which would I put on my own roof?
Honest answer for 2026: for most houses I'd fit a heat pump, and if you want the sun heating your water, put the money into PV panels and run the heat pump through the middle of the day. It is cheaper to install, the rebates are simpler, there is no roof work, and it does not care that your block faces south. I cover it in heat pump hot water systems explained.
Solar hot water still wins in a few places. A big household with a clear north roof and heavy hot water use gets more out of a solar collector than out of the same roof area of PV. A courtyard block in Gregory Hills where a heat pump would sit under a bedroom window: solar is silent. And an existing solar system with a sound tank is worth repairing, because the collectors usually outlast the tank. Planning a renovation or new build? Tell me early and I'll design the roof and pipe runs around it.
When to call a plumber
Call if your solar system is lukewarm in summer (usually a failed pump, a stuck controller, a broken tube or a tired booster element), if the booster runs all the time, if the relief valve on a roof tank runs constantly, or if water is coming off the roof where it shouldn't. None of those is an after-hours emergency; the booster keeps you in showers until business hours. Call before you buy, too. The cheapest solar quote in the letterbox is nearly always a close coupled kit with no frost protection. Done right. Done once.
Installing, replacing or repairing a solar hot water system is licensed plumbing work in NSW; the valves and the compliance certificate are part of the job, not extras. Monarch Civil & Plumbing covers South West Sydney and the Macarthur region from our base in Austral. For a solar or heat pump hot water installation, a second opinion on a quote, or any other plumbing service, from a plumber in Oran Park to Camden, ring 0455 222 292. As a plumber across South West Sydney I have been up on most of its roof types, and I will tell you straight whether solar suits yours.
Related guides: hot water system installation cost.
Need it sorted? Ring 0455 222 292 any hour or book online. Monarch Civil & Plumbing is a hot water plumber, no call-out fee: repairs where they are worth it, same-day replacement where we can, and the NSW rebate sorted.
No hot water in Campbelltown, Liverpool or Camden?
Campbelltown has its own page: hot water service Campbelltown. For Liverpool, Camden and the rest of South West Sydney start with hot water systems, then the suburb pages plumber Liverpool and plumber Camden. Same-day replacement for common electric and gas sizes where stock allows, no call-out fee, NSW rebate sorted for heat pumps.
Frequently asked
How does solar hot water work on cloudy days and in winter?
The collectors still pick up some heat on an overcast day, just less of it, and the booster covers the shortfall. An electric booster is an element in the tank; a gas booster is a continuous flow unit after the tank that only fires when the water is below temperature. In a Sydney winter expect the booster to do most of the work in June and July and very little from October to March, provided it is on a timer or off-peak so the sun gets first go.
Evacuated tube vs flat plate: which is better in Sydney?
For a north facing roof in the older suburbs, a good flat plate system is fine and costs less. Evacuated tubes hold their output better on cold, overcast days, weigh less, and carry no water in the tubes, so frost cannot split them. On the Camden and Campbelltown side, where frosts are regular, I lean towards evacuated tubes or a frost rated flat plate system with a glycol loop.
Is there a rebate for solar hot water in NSW?
Two can apply. Federal STCs are available for solar water heaters on the Clean Energy Regulator's register, under 700 litres and installed by a licensed plumber; the installer claims them and takes them off the price. The NSW hot water upgrade incentive lists electric boosted solar replacing an existing electric or gas water heater, through an accredited provider with a minimum co-payment. Gas boosted solar only qualifies where it replaces an existing gas heater. Check the official page, because the rules move.
How much does a solar hot water system cost in Sydney?
I quote it on inspection, because the spread is wide. The price moves with the collector type, close coupled or split, the booster, a single or two storey roof, any roof strengthening, frost protection and the solar rated tempering valve. As a rule it lands above a heat pump, which Sydney 2026 price guides put at $3,450 to $6,900 before rebates, and well above a plain electric tank at $920 to $2,875.
Solar hot water vs heat pump: which is cheaper to run?
Both are cheap to run compared with a plain electric tank. A well set up solar system with the booster on a timer uses very little power outside winter. A heat pump uses roughly a quarter to a third of the electricity of an element tank all year, and paired with PV panels and a daytime timer it gets close to free. For most houses the heat pump wins on total cost once rebates and installation are counted; solar wins with a big household and an ideal roof.
Why is my solar hot water not getting hot?
Start with the booster: if it is switched off or the timer is wrong you will feel it first in winter. In summer, lukewarm water usually means the circulating pump or controller on a split system has failed, a tube or panel is damaged, or a tempering valve has stuck and is mixing in too much cold. A relief valve running constantly points to pressure or a tired valve. All of it is a business-hours job for a licensed plumber.
Licensed plumber and drainer based in Austral, 13+ years in the trade, working across Liverpool, Fairfield and the Macarthur region. About Paul