Quick answer
Yes, but not by connecting a heat pump to whatever radiators are already there. An air-to-water heat pump makes water far cooler than a boiler does, so it suits radiant floors and generously sized cast-iron radiators and struggles with fin-tube baseboard. In most local hydronic homes the practical route is ductless heads for heating and cooling, with the boiler kept as backup.
A heat pump can replace a boiler, and in a house with in-floor radiant heat it does so without compromise; with fin-tube baseboard it usually cannot. The question is never about the heat pump — it is about the emitters already installed in your rooms, and whether they can deliver enough heat with much cooler water running through them. That single constraint decides the whole project in century homes from Westdale and Dundas to the older streets of Aldershot.
The temperature gap is the whole problem
A gas boiler sends water out at high temperature, historically in the 70–80°C range on older cast-iron systems. An air-to-water heat pump is efficient when it makes water in roughly the 45–55°C range, and its efficiency falls sharply as you push it hotter. A radiator's output depends on the difference between its surface and the room, so the same radiator that heated a bedroom easily on hot boiler water may deliver only a fraction of that on heat pump water. Nothing is broken — the emitter is too small for the new temperature.
Which emitters can work at heat pump temperatures
- In-floor radiant: the best match by a distance. It was designed for low water temperatures, and a heat pump runs it at exactly the point where it is most efficient.
- Cast-iron column radiators in pre-war houses: often oversized for the room by the standards of the day, which is exactly the surplus that low-temperature operation needs. Frequently workable after a room-by-room check, sometimes with one or two radiators replaced.
- Modern flat panel radiators: sized for the original boiler temperature, so they usually need to be swapped for larger panels — straightforward, but a real line on the quote.
- Fin-tube baseboard: the hardest case. Output collapses at lower water temperatures and there is rarely enough wall length to add more.
- Hydro-air fan coils: generally fine, since a coil in an airstream tolerates cooler water better than a radiator does.
Find out whether your boiler also makes your hot water
Many hydronic homes run domestic hot water off the same appliance, either through a combi boiler or an indirect tank. Remove the boiler and you have removed the shower supply as well, so the project quietly becomes two projects. Budget for a water heater in that case, and decide early whether you are keeping a gas connection at all — the answer changes the plumbing, the venting and the monthly fixed charge on the gas account.
The route most local hydronic homes take instead
For a Hamilton century home or a downtown Burlington brick house with radiators, the pragmatic answer is usually ductless heat pump heads: they heat and cool, they need no ductwork, and they leave the hydronic system in place for the coldest weeks. Radiators never gave those houses air conditioning, so this route solves a summer problem at the same time — an argument no boiler replacement can make. Details on how ductless heating performs are in are ductless heat pumps good for heating, and Hamilton century home heating covers the wider retrofit picture.
Practical considerations before committing
- Air-to-water equipment is a specialty install with a smaller pool of trained installers than ducted or ductless systems — ask directly who has commissioned one and where.
- A buffer tank is usually required so the compressor is not short-cycling against a small water volume.
- Ontario's hard water is an issue for any hydronic system; a closed loop is largely protected, but any domestic hot water side is not.
- Electrical service matters even more here, because you are removing gas heat entirely rather than adding a second stage.
- A single-zone ductless system installs for $4,000–$7,000, three to four zones for $10,000–$16,000+, which gives you a comparison point when an air-to-water quote arrives.
When keeping the boiler is the better answer
If your boiler is relatively young and the house is comfortable, keeping it and adding heat pump heads for shoulder-season heating and summer cooling is often the cheapest good outcome. If it is at the end of its life, the decision is open — see how long a boiler lasts for the repair-or-replace side before you commit either way.
ZK Mechanical services boilers and installs heat pumps, so we have no reason to push you toward one answer. For a walkthrough of your radiators and an honest read on what your house can do, see heat pump installation in Hamilton or book a visit.