Almost every heat pump conversation we have in Stormont, Dundas and Glengarry starts with the same worry: "That's fine for Toronto, but will it actually keep my house warm when it hits minus 25?"
It's a fair question. Most heat pump content online is written for milder climates, and older heat pumps genuinely did struggle in deep cold. But the technology changed, and the honest answer for an SD&G home is: yes, a properly specified cold-climate heat pump will keep your house warm through our winters — as long as three things are done right. Here's what's actually going on.
"Cold-climate" is a specific thing, not a marketing word
Not every heat pump is built for Eastern Ontario. The ones that are get called cold-climate heat pumps (CCHPs), and they're a different machine from the units you'd put in Vancouver.
The key difference is the compressor. A cold-climate unit uses a variable-speed inverter compressor that ramps up output as the temperature drops, instead of a single-speed compressor that just switches on and off. That's what lets a good CCHP hold most of its heating capacity down to around -25°C, and keep producing usable heat even colder than that.
When you're shopping, the number that matters is the rated heating capacity at low temperature — how many BTUs the unit still puts out at -15°C and -25°C, not just its capacity on a mild day. A unit that makes strong heat at 8°C but collapses at -20°C is not a cold-climate unit, no matter what the brochure says.
The part nobody explains: capacity falls as it gets colder
Here's the physics that trips people up. A furnace makes the same amount of heat whether it's 0°C or -30°C outside — it's just burning fuel. A heat pump moves heat from the outdoor air into your house, so the colder it gets, the harder it works and the less heat it can move.
This means every heat pump has a balance point: the outdoor temperature below which it can no longer keep up with your home's heat loss on its own. For a well-sized cold-climate unit in an average SD&G home, that balance point often lands somewhere around -20°C to -25°C.
That's not a problem — it's expected, and it's exactly what backup heat is for.
What happens on the three coldest nights of the year
Our design temperature in this part of Eastern Ontario is roughly -24°C to -27°C, and a polar-vortex snap can push us past that a handful of nights each winter. On those nights, one of two things handles the gap:
- Electric backup heat. All-electric heat pump systems include electric resistance heat that kicks in automatically when the heat pump can't keep up. Your house stays warm; your hydro bill ticks up for those specific hours.
- A backup furnace (dual-fuel). If you keep your existing propane, gas, or oil furnace, the system switches to it automatically on the coldest nights. This is often the smart setup here — we wrote a whole piece on dual-fuel heat pump systems if you want the details.
Either way, you're never left cold. The heat pump does the heavy lifting for the 95%+ of winter that sits above its balance point, and the backup covers the extremes.
The three things that have to be done right
When someone tells you "heat pumps don't work up here," they're almost always describing a system where one of these went wrong:
- Sizing. The unit has to be matched to your home's actual heat loss with a proper Manual J load calculation — not a rule of thumb, not "whatever matches the old furnace." An undersized unit runs out of capacity too early; an oversized one short-cycles and wastes money.
- Equipment selection. It has to be a genuine cold-climate model with the low-temperature capacity to match our design temperature, from a manufacturer that stands behind it.
- Installation and controls. The backup heat has to be wired and configured to hand off correctly, the refrigerant charge has to be dialed in for cold operation, and the balance point set for your home and your energy costs.
Get those three right and the "heat pumps don't work in Eastern Ontario" story simply doesn't happen to you.
The comfort difference people don't expect
One thing that surprises new heat pump owners: the house feels more consistently comfortable, not less. A furnace heats in big blasts — it roars to 22°C, shuts off, drifts down a couple degrees, then roars again. A variable-speed heat pump runs low and slow, holding a steady temperature with far less swing. Rooms that used to be the "cold room" tend to even out.
The air from the vents is cooler than furnace air (closer to skin temperature than a hot blast), which throws some people off at first. It's not producing less heat — it's producing it more gently and continuously.
So, will it keep you warm?
Yes — a right-sized, cold-climate heat pump, properly installed with the correct backup, will keep an SD&G home warm through every night our winters throw at it. The failures you hear about are almost always sizing, equipment, or installation failures, not a limit of the technology.
If you want a straight answer for your specific house — square footage, insulation, current heating system, and where your balance point would land — call us at (613) 363-9011 or request a quote. We'll run the numbers honestly, and if a heat pump isn't the right call for your home, we'll tell you that too. You can also read more about our heat pump installation service.