Roof-mounted evacuated-tube solar collectors feed your hydronic network — free heat from the sun, paired with an insulated thermal store so you have hot water and heating on demand, day or night.
Solar hydronic heating uses roof-mounted evacuated-tube or flat-plate collectors to heat a glycol-water fluid, which charges an insulated thermal store that feeds radiators, underfloor loops and hot water. A properly sized array of roughly 8–20 m² supplies 50–80% of annual hydronic heating demand and 60–90% of hot water, with a heat pump, gas or electric backup covering the rest. AHHAC designs and installs solar hydronic systems in Sydney and across NSW, VIC, QLD & ACT.
Reviewed by the AHHAC Technical Team — licensed plumbers & hydronic engineers, NSW Lic 262528C.How we write & review
Solar hydronic (also called solar thermal) heating differs from typical solar panels. Where rooftop solar PV generates electricity, solar thermal collectors heat a glycol-water fluid directly inside the tubes — and that hot fluid feeds your hot water cylinder, your radiators, your underfloor loops, or all three.
It's the most efficient way to use Australian sun for the comfort layer of your home. A properly sized array supplies 50–80% of your annual hydronic heating demand and 60–90% of your hot water demand.
Sun shines on the rooftop solar collectors and heats the glycol-water fluid inside the evacuated tubes. The fluid is pumped through copper heat-exchange coils inside an insulated thermal store tank installed in your service area.
Because evacuated tubes don't require direct sunlight to perform — they capture diffused light too — the system continues to produce useful heat through cooler seasons and overcast days. The insulated tank holds water at the required temperature for several days, smoothing out cloudy stretches.
Hot water from the thermal store is then fed on demand to your hot water taps, your hydronic radiators, or your underfloor heating loops. Continuous circulation through the collectors ensures hot water is always available.
There are four main reasons our clients choose solar hydronic — and once they're in, they almost never go back to gas-only.
First, it's environmentally friendly. Solar is an emission-free source of energy, and a system properly sized to your home will dramatically decrease your greenhouse gas emissions over its 30+ year life.
Second, it's cheaper to run. Once installed, the energy itself is free — your only ongoing cost is a tiny circulation pump.
Third, it's low-maintenance. Solar thermal technology is mature and simple. With minimal moving parts, the systems require very little upkeep beyond an annual glycol-fluid check.
Fourth, you get consistent hot water. Continuous heating combined with thermal-store storage means you have hot water available whenever you need it — even if the sun hasn't shone for days.
Thermal store tank designed for solar systems running with a gas or oil boiler backup. Hygienic stainless heat exchanger and integrated pump set.
Thermal store engineered for solar paired with an electric heat pump — combines two energy sources into a single buffer for whole-home heat and hot water.
Pressurised flat-plate solar collectors for residential roof-mounted installs. Compact and easy to integrate with existing roof structures.
Drain-back configuration for harsher climates — system drains automatically when collectors aren't in use, eliminating freeze risk.
The awkward truth about solar hydronic heating is that collectors produce the most heat in January, when nobody wants warm floors. Size an array to cover a large share of July heating and, unless the design deals with it, you will have a roof full of very hot fluid and nowhere to send it all summer. Handling that surplus is the part of solar thermal design that separates systems that last for decades from ones that cook their glycol within a few years.
Solar hydronic is not for every home. Heavily shaded roofs, south-facing roof planes and small households with low heating loads usually get a better return from rooftop PV driving a heat pump, and we will model both before recommending either. Where it does fit, typically larger homes with good north-facing roof space and a year-round hot water or pool load, payback of 6–10 years is realistic.
For the numbers, read our solar hydronic heating ROI guide, compare an air-source heat pump as the backup or alternative, and see our thermal store and tank options.
Written from on-site experience by the AHHAC Technical Team.
AHHAC's in-house design and service team — licensed plumbers and hydronic engineers (Lic 262528C) who have designed and installed 2,400+ hydronic heating, cooling and hot water systems across Australia since 1998.
We design solar hydronic heating from a room-by-room heat-loss calculation, install it with our own licensed plumbers to AS/NZS 3500 (plumbing) and AS/NZS 5601 (gas), commission and document it, and service it for the life of the system. Nothing is subcontracted out.
In Australian conditions, a properly sized solar thermal array supplies 50–80% of your annual hydronic heating demand and 60–90% of your hot water demand. The remainder is covered by a backup heat source (gas, heat pump or electric).
Solar thermal is roughly 3–4× more efficient per square metre of roof for water heating specifically. We often install both — PV for general electricity (powering a heat pump), thermal for direct heat — for the best overall system.
Yes — solar thermal systems are eligible for Small-scale Technology Certificates (STCs) under the Australian Renewable Energy Target. The value depends on the model, your postcode and the year (STCs decline each year to 2030), so we calculate it at quote and handle the paperwork.
"AHHAC delivered our 22-zone underfloor system on time, on budget and to spec. The crew were tidy, the documentation was thorough, and the commissioning was textbook."
"We've worked with AHHAC for 17 years. They've installed and serviced our hot water plant across three commercial buildings — and they pick up the phone on weekends."
"Three mobs quoted us; AHHAC's design was the only one based on a proper heat-loss calculation. The system runs beautifully — the others would've been oversized and expensive."