Hydronic heating vs reverse cycle air conditioning: which should you choose? (2026)

A reverse-cycle air conditioner and a hydronic heat pump use the same refrigeration cycle: they pull heat out of the outside air and move it indoors, which is why both are so efficient. The difference is what they move that heat into.

Reverse-cycle air conditioning heats air. A split system has one indoor wall head per room; a multi-split runs several heads off one outdoor unit; a ducted system blows warm air through ceiling ducts and vents to the whole house. Heat arrives by convection — warm air pushed around by fans.

Hydronic heating heats water. A hydronic heat pump warms water to roughly 35–55 °C and circulates it through underfloor loops, panel radiators or fan coils. Floors and radiators warm you mainly by radiation; fan coils behave more like an air conditioner. Same physics at the outdoor unit, a very different experience in the room.

How the three main options compare for a typical 200 m² Australian home:

Reverse cycle, almost every time. A single split system is the cheapest way to add heating to a room, and multi-splits scale that to several rooms off one outdoor unit. For a typical 200 m² home, ducted reverse cycle usually installs for around $14,000–$22,000.

Hydronic sits higher. A full-home radiator system typically costs $12,000–$30,000, while in-slab underfloor with a heat pump for a 200 m² home usually lands around $30,000–$55,000. The gap narrows in a new build — underfloor pipe laid before the slab pour is a modest incremental cost — and widens in a finished home where every pipe has to be routed around existing walls and floors. If upfront cost decides it, reverse cycle wins; our ducted vs hydronic heating comparison sets out how that trade-off plays out over a system's full life.

This is where marketing on both sides gets loose, so here's the straight version. According to the Australian Government's energy.gov.au heating and cooling guidance, reverse-cycle air conditioners on the Australian market deliver roughly 3 to 6 units of heating for every unit of electricity. A hydronic heat pump does much the same, at a COP of 3.5–5.5. At the outdoor unit they're in the same league — and both are far cheaper to run than electric resistance heaters or an electric boiler.

The real differences come from how the heat is delivered:

• Heating one or two rooms: a modern split system is very hard to beat. For a single living area, it's usually the cheapest heating you can buy and run.
• Ducted losses: ducted systems push warm air through roof-space ducts, where some heat is lost before it reaches the room, and they often heat more of the house than you're using.
• Comfort at a lower setting: radiant heat often lets people feel comfortable a degree or so cooler. energy.gov.au's winter energy advice recommends 18–20 °C and notes each extra degree adds roughly 5–10% to heating energy use.
• Thermal mass: in-slab underfloor stores heat, so it can be charged on daytime solar and coast through the evening.

So the cheapest way to heat a house in Australia is a heat pump of some kind, correctly sized, in a well-insulated and draught-sealed home, heating only the zones you use. For one or two rooms, that's a split system. For whole-home heating through a long, cold winter, a heat-pump hydronic system typically runs cheaper than ducted — and it outlasts it.

This is the biggest difference you'll actually feel. Air-based heating warms the air, and warm air rises: the ceiling gets the heat first, the floor stays cool, and the warmth pulses as the fan cycles. Ducted systems also create gentle draughts near vents and return grilles. Plenty of people describe it as warm face, cold feet.

Hydronic works the other way round. Hydronic underfloor heating turns the whole floor into a low-temperature radiator, so warmth starts at your feet and stays even to head height. Radiators heat through a mix of radiation and gentle convection, with no fans. The trade-off is response: in-slab underfloor takes hours to change temperature, so it suits households that run a steady schedule. If you want heat in minutes, radiators (15–25 minutes) or a split system respond far faster.

Every heat pump has an outdoor unit, so noise outside the house is comparable. Inside is a different story. A split or ducted system always has a fan running while it heats; good modern heads are quiet — some drop to about 26 dB(A) in sleep mode — but ducted return-air grilles and vents can be noticeable in bedrooms. Underfloor and radiator systems have no indoor fans at all; the only moving part is a circulating pump in the plant area.

On air quality, air conditioners recirculate room air through filters that need regular cleaning, and ducts can collect dust over the years. Hydronic floors and radiators don't move air, so they don't stir up dust, pet hair or pollen — the main reason allergy and asthma households choose them. The honest caveat: hydronic heating doesn't filter or ventilate, so a tightly sealed home still needs good ventilation.

If summer is your main problem, reverse cycle is the natural choice. Air conditioners cool quickly, dehumidify as they go and handle 40 °C afternoons without fuss. A hydronic system only cools if it's designed to:

• Hydronic fan coils run on chilled water from a reversible heat pump, and cool and dehumidify much like a split-system head.
• Underfloor cooling runs chilled water (around 8–14 °C) through the same floor loops for gentle, silent radiant cooling — but it needs dew-point control in humid weather and won't pull a hot room down quickly.
• Radiators and skirting can't cool at all.

So a radiator-only hydronic system means you'll still want air conditioning for summer. If you want one system for both seasons, design hydronic cooling systems in from day one rather than bolting them on later.

A ducted reverse-cycle installation typically lasts around 12–18 years before major replacement, and split systems are an appliance purchase in a similar range. A hydronic system splits in two: the pipework and emitters carry a 30+ year design life, while the heat pump — the part that wears — has a 15–20 year design life and is replaced on its own, without touching floors or walls.

Visually, splits put a head on the wall of every room you heat, and ducted adds ceiling vents and a return-air grille. Hydronic radiators also use wall space, but slim European panels sit neatly under windows or can be chosen as a design feature, and underfloor is completely invisible. In cold-climate markets, buyers also tend to see hydronic as a premium feature.

Reverse cycle is the easier retrofit. A split system needs a wall head, an outdoor unit and a short refrigerant and drain run. Ducted needs usable roof space or subfloor for the ductwork, which can rule it out in some double-storey homes, flat-roofed designs and heritage houses.

Hydronic retrofits are very achievable but more involved. Radiators are the go-to: fed by pipes routed through the subfloor, roof space or cupboards, and typically installed in 1–3 days with no floor works. Underfloor in an existing home means an in-screed system laid where floors are being replaced, which adds a little floor height. If you're mid-renovation with the floors up anyway, the maths swings towards hydronic.

Both systems are all-electric, so both pair well with rooftop solar — and both let you drop a gas connection and its supply charge. The difference is storage. An air conditioner heats or cools in the moment; when the sun goes down, your solar contribution stops. In-slab hydronic underfloor holds heat for hours, so a system scheduled to work harder in the middle of the day effectively banks solar warmth for the evening. Air conditioning can borrow a version of the same trick: on solar, pre-heat or pre-cool the house in the mid-afternoon so the system has less to do once the panels stop producing. Either way, a heat pump running on your own solar is the lowest-cost way to keep an Australian home comfortable.

Plenty of the homes we design don't choose one. The most common combinations:

• Hydronic heating plus split systems. Underfloor or radiators for silent winter comfort through the house, with reverse-cycle splits in the two or three rooms that get hot in summer.
• One reversible heat pump, two jobs. A hydronic heat pump heats floors or radiators in winter and sends chilled water to fan coils in summer — one outdoor unit, one network, no separate air conditioning.
• Hydronic heating plus a Maxa Total-One. The Maxa Total-One runs up to three reverse-cycle indoor heads and heats a 190-litre hot water cylinder from one outdoor unit, at a COP of up to 3.9. Alongside hydronic heating, it covers summer cooling for bedrooms and makes your hot water — with heat recovered while cooling sent into the tank.

Choose reverse-cycle air conditioning if…

• cooling matters more than heating, as in Brisbane and most of Queensland;
• you need to heat one or two rooms, or you're working to a tight budget;
• you're renting, or likely to sell within a few years;
• you're retrofitting a finished home with no floor or wall works planned.

Choose hydronic heating if…

• you live with a long, cold heating season — Canberra, Melbourne, the Blue Mountains, inland NSW;
• you're building, or renovating with floors up;
• comfort, silence and air quality are the priority, or someone in the house has allergies;
• you'll own the home long enough to benefit from a 30+ year system.

Our usual starting point by city

• Canberra: hydronic heating leads, ideally on a cold-climate heat pump; add splits or fan coils only where summer heat is a real problem.
• Melbourne: hydronic for living areas and bedrooms, with a split for an upstairs room that bakes in January.
• Sydney: genuinely split — comfort-led and new-build clients lean hydronic, budget retrofits lean reverse cycle.
• Brisbane: reverse cycle, or a reversible hydronic heat pump with fan coils if you want one quiet system for both seasons.

Combine them if…

you want the best winter comfort and strong summer cooling. In a cold climate such as hydronic heating in Canberra, hydronic usually leads and air conditioning fills the gaps; for hydronic heating in Sydney, a combined design is often the sweet spot. Whichever way you go, size it from a room-by-room heat-loss calculation, not a rule of thumb.

• The Australian Government's energy.gov.au guidance on reverse-cycle air conditioner efficiency and winter thermostat settings, cited above.
• Manufacturer datasheets for the heat pumps, fan coils, radiators and air-conditioning systems we supply, including Maxa.
• AS/NZS 3500 (plumbing) and AS/NZS 5601 (gas installations), the standards we install to.
• AHHAC design, install and service experience across 2,400+ hydronic systems since 1998, including combined hydronic and reverse-cycle projects.

This guide was written and reviewed by the AHHAC Technical Team — licensed plumbers and hydronic engineers (NSW Lic 262528C). Prices reflect our 2026 installs, and we'll next review it before winter 2027.