The brief
The owners of a solid 1970s brick home in Canberra's inner south had had enough of their ageing gas heating: rising bills, an old boiler nearing the end of its life, and a desire to go all-electric and pair the home with the rooftop solar they'd just installed. They came to AHHAC with a clear goal — get off gas, keep the whole house genuinely warm through a Canberra winter, and cut the running cost — but they'd been warned by more than one contractor that "a heat pump won't cope with Canberra's cold." They wanted proof it would.
The challenge
Canberra is the hardest climate in the country for this decision. With well over 2,000 heating-degree-days, hard frosts and mornings that regularly drop below −5 °C, the ACT is exactly where an under-specified heat pump does struggle — fading in output and falling back on expensive electric-element backup just when the home needs heat most. The myth that "heat pumps don't work in the cold" comes from exactly those under-rated units. The challenge here was to specify and size a system that would hold full output and a high efficiency through real Canberra frosts, retrofit it into an occupied home, and then measure the result to settle the question. See the wider climate picture on our hydronic heating Canberra page.
The design
The heart of the system is a Maxa i-290 — an R290 monoblock heat pump rated to −25 °C ambient, chosen precisely because it holds output far below Canberra's coldest morning instead of fading. We ran a full room-by-room heat-loss calculation to Canberra's real design temperature (not a Sydney one), then sized the i-290 and the emitters to that load. The home kept its existing radiators where they were correctly sized and gained several generously sized replacement panels where they weren't, all re-balanced to run at a low flow temperature so the heat pump stays in its most efficient band. The result is an all-electric system designed to run hard, efficiently, all winter. This is the same approach we detail on our heat pump hydronic heating Canberra page.
Sizing to the true design temperature is the step that makes or breaks a cold-climate system — get it wrong and the home is cold on the worst mornings, or the plant is oversized and short-cycles. It's the discipline behind every AHHAC Canberra job.
The install
Because it was a retrofit into an occupied home, we staged the work to keep the family warm throughout: the new heat pump and re-balanced radiator circuit were installed and commissioned before the old gas plant was disconnected and removed. Our in-house crew handled the refrigerant pipework, the electrical works and the integration with the home's solar, and set the system up for weather-compensated operation so the flow temperature tracks the outside conditions — running cooler on milder days for extra efficiency. The gas was disconnected entirely, removing the daily supply charge for good.
The result
Through its first full Canberra winter, the system was monitored — and it settled the argument. It logged a measured seasonal COP of 3.9: every kilowatt of electricity delivered 3.9 kilowatts of heat, in exactly the alpine-zone climate the owners had been told would defeat a heat pump. On the coldest morning of the season, −6 °C, the home held its set temperature in every room with no drama and no reliance on backup elements. Total heating running cost came in around 55% below the old gas system before solar; with the rooftop array covering much of the daytime load, the effective cost fell further still. The owners describe the comfort as a step change from the old system — even, silent warmth everywhere, not just near the vents.
The takeaway is the one we make on every cold-climate job: a correctly specified, correctly sized heat pump doesn't just "cope" in Canberra — it's the lowest-running-cost, lowest-carbon way to heat a home through an ACT winter. For the numbers behind it, see our Canberra running-costs guide; for the climate and policy context, our guide to hydronic heating in Canberra and the cold capitals.