---
title: "Heat Pump Hydronic Heating: A Melbourne Homeowner's Guide for 2026"
date: 2026-10-01T07:00:00+10:00
author: Darren Burch
canonical_url: "https://sogeo.com.au/blog/heat-pump-hydronic-heating-melbourne-guide"
section: Pages
---
![Stiebel Eltron Air Sourced Heat Pump Cascade]()

#  Heat Pump Hydronic Heating: A Melbourne Homeowner's Guide for 2026 

Heat pump hydronic heating swaps the gas boiler for an electric heat pump and keeps the radiant comfort of hot water heating. This guide covers how it works, whether your existing radiators can stay, what it costs to install and run in Melbourne, and the design mistakes that leave a home cold.

 

 

 

 **The short answer.** Heat pump hydronic heating uses an electric air-to-water heat pump, instead of a gas boiler, to heat the water that runs through your radiators, underfloor pipes or fan coils. It is the efficient form of electric hydronic heating: a well-designed system delivers 4 to 5 units of heat for every unit of electricity. In Melbourne, a SóGeo swap from gas boiler to heat pump starts at $15,000 when your existing radiators and pipework stay, and a typical home then spends about $900 to $1,350 a year to run it, against about $4,100 on gas.

**At a glance**

- A heat pump can run most existing gas hydronic systems. A room-by-room heat-loss calculation decides which radiators stay and which need a larger panel.
- It is the efficient way to make hydronic heating electric. An electric element boiler turns one unit of electricity into one unit of heat; a well-designed heat pump turns it into four or five.
- Sizing comes from the heat-loss calculation, not a rule of thumb. Undersized and oversized units both waste money.
- Most Melbourne homes suit air source. Geothermal earns its premium on larger homes, rural and coastal sites, and homes with a pool.
- When a heat pump leaves a house cold, the cause is almost always design: the wrong size, water run too hot, or a system never balanced.

## What is heat pump hydronic heating?

Hydronic heating warms a home with water instead of air. A heat source heats the water, a circulating pump sends it through insulated pipework, and radiators, underfloor loops or fan coils release the heat into each room. It is silent, it moves no dust, and the warmth is even from floor to ceiling. If hydronic heating is new to you, our [guide to how hydronic heating works](/blog/understanding-exactly-how-hydronic-heating-systems-work-the-basics-for-homeowners) covers the basics.

For most of its history in Melbourne, the heat source was a gas boiler. Heat pump hydronic heating replaces that boiler with an air-to-water heat pump. Everything downstream of the heat source works the same way. What changes is how the heat is made.

A gas boiler burns fuel to create heat and tops out near 90% efficiency. A heat pump creates almost no heat itself. It moves heat that already exists in the outdoor air into the water, using a refrigerant cycle, and that is why it delivers more heat than the electricity it uses. The same machine can run in reverse in summer to cool the home through underfloor pipes or fan coils.

## How a heat pump runs a hydronic system

1. **Extraction.** A fan draws outdoor air across a coil filled with refrigerant. The refrigerant absorbs heat from the air, even on a cold Melbourne morning.
2. **Compression.** The refrigerant is compressed, which raises its temperature well above what the water needs.
3. **Transfer.** A heat exchanger passes that heat into the water circuit, and the circulating pump sends the water out to the radiators or floor.
4. **Control.** A weather-compensation controller sets the water temperature from the outdoor temperature: hotter on the coldest days, cooler on mild ones.

That last step matters more than most buyers realise. **Water temperature is what sets a heat pump’s efficiency.** The cooler the water it has to make, the less work it does. On a cold winter morning an air source unit feeding 35°C water still delivers about 3.5 units of heat per unit of electricity; asked for 55°C water on the same morning, that falls to about 2.2. Across a full year, a SóGeo install typically returns a seasonal efficiency (SCOP) of 5 or higher, because the design keeps the water as cool as the rooms allow.

## Can a heat pump run my existing gas hydronic system?

Usually, yes. This is the most common question we are asked, and the answer is better than most people expect.

When most Melbourne hydronic systems went in, few installers ran a proper heat-loss calculation. The common practice was a rule of thumb based on floor area or room volume, and those rules overshoot what most rooms actually lose. So most existing radiators are bigger than the room strictly needs. For a gas boiler that was waste. For a heat pump it is good news, because a radiator with extra surface area can deliver full warmth with the cooler water a heat pump runs best on.

The Stiebel Eltron WPL-A Trend units we install can also reach flow temperatures of 75°C, high enough to drive radiators that older heat pumps could not. We still design to keep the water as cool as possible, because cooler water is cheaper heat.

A SóGeo room-by-room heat-loss calculation usually confirms that most of your radiators can stay exactly where they are. Where a room does need more surface area, we swap the single panel for a double or triple panel of the same length in the same position, so the pipework through your wall or floor stays untouched. In-slab underfloor systems are the easiest conversion of all, because a heated slab already runs on low water temperatures. If your boiler is failing and you are weighing up the options, our post on [whether to repair, replace or switch your hydronic boiler](/blog/hydronic-heating-boilers-repair-replace-or-switch) walks through each path.

## Heat pump hydronic heating vs electric boiler vs gas boiler

Converting gas hydronic heating to electric has two routes, and they are very different.

 Heat pumpElectric element boilerGas boilerHeat per unit of energy4 to 5 units1 unitUnder 1 unit (about 90% efficient)Running cost, typical Melbourne homeAbout $900 to $1,350 a yearAbout 4 to 5 times a heat pumpAbout $4,100 a yearCoolingYes, via underfloor or fan coilsNoNoRuns on rooftop solarYesYes, but uses far moreNoInstalled costFrom $15,000 keeping radiatorsLess than a heat pump$5,500 to $9,000 like-for-likeAn electric element boiler is simple and cheap to fit, but it turns each unit of electricity into one unit of heat, so it runs up roughly four to five times the electricity of a heat pump delivering the same warmth. That is why we do not recommend it as a whole-home heat source. A like-for-like gas boiler swap has the cheapest day-one price and the most expensive decade. The heat pump costs more on the day and far less every winter after it.

## How to size a hydronic heat pump

Sizing is where hydronic heat pumps are won or lost, and it cannot be done from floor area alone.

**We size from a room-by-room heat-loss calculation.** It accounts for your insulation, glazing, orientation, ceiling heights and how the home is used, and it sets both the heat pump capacity and the water temperature each room needs.

**Undersized is cold; oversized is wasteful.** An undersized heat pump runs flat out on the coldest mornings and still falls short. An oversized one short-cycles, switching on and off, which costs efficiency and wears the compressor. Both drag the SCOP down.

**Model numbers are not the whole story.** The WPL-A Trend range covers most homes in three sizes, and each one modulates across a wide output range at the standard test point (7°C air, 35°C water): 2.76 to 10.97 kW for the 10.2, 3.69 to 13.92 kW for the 13.2 and 5.11 to 19.64 kW for the 17.2. The 10.2 runs on a single phase supply; the 13.2 and 17.2 need three phase. The right model comes from the heat-loss calculation, never from the box.

## What it costs to install and run in 2026

**Installing.** A straightforward gas boiler to heat pump swap that keeps your existing radiators starts at $15,000. Most installs run higher with home size, scope, hot water integration and any radiator or insulation upgrades the heat-loss calculation identifies. Putting hydronic heating into a home that has none is a larger job, quoted from the drawings. SóGeo gives a fixed quote after a site visit and heat-loss calculation.

**Running.** A typical Melbourne home running its heating 10 hours a day through a five-month winter spends about $900 to $1,350 a year on electricity with a heat pump, against about $4,100 a year on a gas boiler. Most homeowners save over $2,500 a year, and more with rooftop solar.

Our [hydronic heating cost guide](/blog/how-much-does-it-cost-to-switch-from-gas-to-hydronic-heat-pumps) has the full breakdown, including per square metre rates for underfloor systems and how running costs are worked out.

## Air source or geothermal?

Both are heat pump hydronic heating. The difference is where the heat comes from.

**Air source is the right answer for most Melbourne homes.** Lower upfront cost, no ground works, and a SCOP of 5 or higher when it is designed properly. It suits boiler swaps, renovations and new builds. See our [air source heat pumps](/air-source-heat-pumps) page.

**Geothermal draws its heat from a buried ground loop instead of the air.** Ground temperatures stay stable all year, so a ground source heat pump holds a COP of 5 to 7 through the coldest morning and the hottest afternoon, and the buried pipework lasts 50+ years. Our own projects have measured SCOPs of 8.1 at Coimadai, 7.4 at Invermay, 5.2 at Port Campbell and 5.1 on the Main Ridge lake loop. Geothermal earns its premium on larger homes, rural and coastal properties, homes with a pool, and sites where the electrical supply is tight. SóGeo is the exclusive Victorian distributor and installer of the Stiebel Eltron WPE geothermal range; see our [ground source heat pumps](/ground-source-heat-pumps) page.

## The downsides, honestly

- **Higher upfront cost than a like-for-like gas boiler or ducted system.** The running cost earns it back, but the day-one number is real.
- **It runs low and slow.** A hydronic heat pump is designed to run steadily at low output, not to blast heat on and off. That is where its efficiency comes from, but it suits people who leave the heating on through the day rather than firing it up for an hour.
- **Performance follows the building.** A draughty, poorly insulated home needs more heat and hotter water. We factor the envelope into every design before choosing the capacity.
- **Standard panel radiators heat only.** If you want cooling as well, it comes through hydronic underfloor or fan coils, driven by the same heat pump. Our comparison of [underfloor heating and radiators](/underfloor-vs-radiators-melbourne) covers the trade-offs.
- **Summer heatwaves cut air source cooling efficiency.** On a 35°C day an air source unit’s cooling COP can fall to 2.5, and below 2 on a 40°C+ day. Geothermal is unaffected.
- **There is an outdoor unit.** The WPL-A Trend has a sound power level of 48 to 49 dB(A) depending on the model, and it needs a sensible position away from bedroom windows and boundaries. Indoors, the system is silent.

## Why a house can feel cold with a heat pump

“My house is cold with a heat pump” is one of the most searched complaints about this technology. In our experience the equipment is rarely the cause. The usual culprits are:

1. **The unit was sized by guesswork.** No heat-loss calculation, so it cannot keep up on the coldest mornings.
2. **The water is too cool for the emitters.** Radiators that were never checked against the heat pump’s lower water temperature cannot put enough heat into the room.
3. **The water is too hot for the heat pump.** The installer turned the flow temperature up to compensate, which drags efficiency down and running costs up.
4. **No weather compensation, or it was never tuned.** The system cannot adjust as the weather changes.
5. **The system was never balanced.** Some rooms get most of the flow while others starve.
6. **Air and sludge in an old circuit.** A system that has gone years without attention loses output. [Power flushing](/power-flushing-hydronic) restores it.

Every one of these is a design or commissioning problem. It is why an installer who quotes a heat pump swap without measuring heat loss is guessing with your comfort and your running costs.

## Hot water and cooling from the same system

**Hot water.** A hydronic heat pump can also take over your domestic hot water with a stainless steel tank, typically adding $4,000 to $5,000 to the project. It is far more powerful than a dedicated hot water heat pump, so it reheats the tank in about an hour rather than four or five. One plant, one electric system, no gas connection.

**Cooling.** In summer the heat pump reverses and cools the home through underfloor pipework or fan coils. See [hydronic underfloor cooling](/hydronic-heating-cooling/hydronic-underfloor-cooling-efficient-comfort-for-your-home).

## What happens on a SóGeo project

1. **Site visit.** We look at the home, the existing system if there is one, the switchboard and where the outdoor unit can go.
2. **Heat-loss calculation.** Room by room. It sets the heat pump size, the water temperature and which radiators stay.
3. **Design and fixed quote.** You get a fixed price, not an estimate.
4. **Install.** The gas boiler is disconnected and removed, the heat pump goes in, pipework is modified where needed and any radiator upgrades are fitted.
5. **Commissioning.** Weather compensation is tuned and the system is balanced to hit its SCOP target.
6. **Service.** An annual service keeps it running at the efficiency it was designed for.

The same team designs, supplies, installs and commissions the system. Director Darren Burch has more than 20 years of hydronic installation experience, 14 of them in Australia, and three generations of hydronic heating in the family, from Ireland to Melbourne. See how we approach [hydronic heating in Melbourne](/hydronic-heating-cooling), or the [Stiebel Eltron hydronic heat pumps we supply and install](/hydronic-heat-pumps).

Have a gas hydronic system, or plans for a new home? Send us the details and we will tell you what a heat pump would need to run it well. [Contact SóGeo](/contact-us).

 

 

  ## Heat Pump Hydronic Heating Questions

  ### Can a heat pump be used for hydronic heating?

 ➕ Yes. An air-to-water heat pump heats the water in a hydronic system in place of a gas boiler, and runs radiators, underfloor heating and fan coils. Most existing gas hydronic systems can be converted. A room-by-room heat-loss calculation confirms which radiators can stay and whether any need a larger panel.

   ### Is heat pump hydronic heating cheaper to run than gas?

 ➕ Yes, in a well-designed install. A typical Melbourne home spends about $900 to $1,350 a year on electricity with a heat pump, against about $4,100 a year on a gas boiler. Pair it with rooftop solar and the daytime running cost falls further.

   ### Is it cheaper to run than ducted heating?

 ➕ Over the life of the system, a well-designed hydronic heat pump costs less to run and delivers better comfort: radiant warmth, no blown air or dust, and silent rooms. Ducted costs less to install, at roughly $9,000 for a premium ducted reverse-cycle system on a standard Melbourne home against a full hydronic radiator system from around $16,000. Our [cost guide](/blog/how-much-does-it-cost-to-switch-from-gas-to-hydronic-heat-pumps) compares the two.

   ### Does a heat pump work in a Melbourne winter?

 ➕ Yes. Melbourne winters are mild by heat pump standards. On a cold morning an air source unit feeding 35°C water still delivers about 3.5 units of heat per unit of electricity, and across the year a SóGeo install typically returns a SCOP of 5 or higher.

   ### Can I convert gas hydronic heating to electric?

 ➕ Yes, and a heat pump is the efficient way to do it. An electric element boiler also works but uses roughly four to five times the electricity for the same heat. A SóGeo gas boiler to heat pump swap that keeps your existing radiators starts at $15,000.

   ### Will I need a new switchboard?

 ➕ We check your supply and switchboard during the site visit. Our free [maximum demand calculator](/tools/maximum-demand-calculator) shows how the choice of heating and hot water changes a home’s electrical demand.

   ### Are there rebates for heat pump hydronic heating in Victoria?

 ➕ There is currently no Victorian rebate for hydronic space-heating heat pump systems. The programs you may have read about apply to hot water heat pumps, which are a separate measure.

   ### How long does a heat pump hydronic system last?

 ➕ The system is engineered for 20 or more years of service. Radiators and pipework routinely outlast the heat source, which is why a swap that keeps them makes sense. An annual service, typically $250 to $450 in Melbourne, keeps it running at its designed efficiency.

  

 

  

## Our Partners

   [ ![Reece](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Reece.png) ](https://www.reece.com.au/)   [ ![Stiebel Eltron](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Stiebel-Eltron.png) ](https://www.stiebel-eltron.com.au/)   [ ![Mitsubishi](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Mitsubishi.png) ](https://www.mitsubishielectric.com.au/)   [ ![Purmo](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/Purmo.png) ](https://www.purmo.com/au)   [ ![Viessmann](https://sogeo.com.au/uploads/suppliers/_AUTOx96_crop_center-center_none_ns/viessmann_wordmark_rgb_1_vitorange.png) ](https://www.viessmann.com.au/)