Ground-source heat pumps draw stable temperatures from below the Earth's surface — the most efficient heat source you can install, with COP 4.5–5.5 and a 50+ year ground loop life.
A geothermal heat pump in Australia draws stable heat from the ground, which sits at roughly 14–18 °C year-round below 2 metres, through buried horizontal trenches or vertical boreholes, and delivers it to a hydronic heating and cooling network at a COP of 4.5–5.5. It costs more to install than air-source but has the lowest running cost and a 50+ year ground loop life. AHHAC designs geothermal systems from Sydney across NSW, VIC, QLD & ACT.
Reviewed by the AHHAC Technical Team — licensed plumbers & hydronic engineers, NSW Lic 262528C.How we write & review
Below 2 metres deep, the ground stays at roughly 14–18°C all year round — regardless of how cold the air gets above. A geothermal (ground-source) heat pump extracts that constant temperature via buried collectors, then concentrates it into your hydronic network.
Because the source temperature is so stable, geothermal heat pumps achieve the highest COPs of any heat source — 4.5 to 5.5. They're more expensive to install up-front but dramatically cheaper to run for the next 50+ years.
Horizontal trench collectors are buried in trenches 1.5–2m deep across an area roughly 2–3× your home's footprint. Cheaper to install, needs available land area, ideal for rural or large suburban blocks.
Vertical boreholes (typically 50–150m deep) take much less land surface but require a drilling rig. Better for built-up sites where land is limited. Slightly higher install cost but identical performance.
Geothermal is the most expensive option to install but the cheapest to run. For high-load homes (4+ bedrooms, cool climates, year-round occupation), the lifecycle cost is unbeatable.
It also reverses cleanly for summer cooling — the same ground loop that delivers heat in winter delivers chilled water in summer. The stable ground temperature makes geothermal the most efficient COOLING option as well.
And the ground loop is silent — there's no outdoor compressor unit constantly running. The only equipment you can hear is the small indoor unit in your service area.
Geothermal is the most efficient heat source we install, but it is also the one where the site has the final say. Before we spend time on a full design, we work through feasibility with the owner, roughly in this order.
When feasibility is marginal, we say so and model an air-source alternative alongside, because the long payback only works if the system genuinely suits the property. When it does stack up, the reward is a near-silent system with steady output through the coldest nights and very efficient cooling in summer, and with no outdoor fan unit there is nothing to find room for down the side of the house.
Compare air-source hydronic heat pumps, read our heat pump hydronic heating guide, see hydronic heating in Canberra, where long cold winters favour high-efficiency sources, or add geothermal hot water to the same ground loop.
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 geothermal heat pumps 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.
For high-load homes (4+ bedrooms, cooler climates), yes. Geothermal achieves COP 4.5–5.5 — the highest of any heat source — meaning lower running costs for the next 50 years. Payback against air-source heat pumps is typically 8–14 years; ground loops last 50+ years.
Horizontal trenches (1.5–2m deep) are cheaper to install but need 2–3× your home's footprint of available land. Vertical boreholes (50–150m deep) take less land but require a drilling rig — typical for built-up sites.
Yes — geothermal heat pumps reverse direction in summer to deliver cooling through the same hydronic network. The stable ground temperature makes geothermal the most efficient cooling option as well.
"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."