Do Heat Pumps Actually Work in a Canadian Winter? The Cold-Climate Data

It’s the number-one objection we hear, and it’s a completely reasonable one: “A heat pump pulls heat from outside air — so how can it possibly keep my house warm when it’s −20°C outside?”

It’s a fair question, and it deserves a real answer backed by data rather than a brochure. So let’s skip the marketing and look at what independent Canadian field testing actually found.

The short answer

Yes — a properly specced cold-climate heat pump keeps producing useful heat through an Ontario winter, including the cold snaps. The key qualifier is “cold-climate” and “properly specced.” A bargain-bin unit sized like an old furnace will disappoint. An engineered cold-climate model, sized with a real load calculation, will not.

What the NRCan testing found

Natural Resources Canada tested cold-climate air-source heat pumps at the Canadian Centre for Housing Technology — a real research facility, not a lab bench. Two findings matter most for an Ontario homeowner.

Comfort held at the coldest temperatures tested

In the centre’s testing, a cold-climate air-source heat pump maintained home comfort at the coldest temperatures encountered — below −21°C — with a coefficient of performance (COP) greater than 1.5.

A COP above 1 means the system is still delivering more heat energy than the electrical energy it consumes. A COP of 1.5 at below −21°C means that even in deep cold, the heat pump was producing 50% more heat energy than the electricity going into it. It hadn’t “given up.”

The efficiency curve, by temperature

NRCan’s mini-split testing mapped the apparent COP across outdoor temperatures, and the curve tells the whole story:

• About 3.1 at +9°C — very efficient in mild weather.
• About 2.3 at −15°C — still delivering more than double its input as heat.
• Close to 2.0 even at −25°C — still strongly net-positive in extreme cold.

That last figure is the one to remember. At −25°C, the heat pump was still delivering roughly twice as much heat energy as the electricity it drew. A −25°C night is colder than a typical winter low across most of the GTA, so a correctly chosen cold-climate unit has real headroom for the conditions Ontario actually throws at it.

What “cold-climate” really means

Not every heat pump is built for this. The term “cold-climate heat pump” (CCHP) refers to units specifically engineered to maintain heating capacity and efficiency in deep cold — typically through variable-speed compressors, enhanced vapour injection and refrigerant designed for low-temperature performance.

For reference, heat pumps meeting the U.S. Department of Energy’s Residential Cold Climate Heat Pump Challenge must keep delivering high heating capacity and efficiency at very cold temperatures — 5°F (about −15°C) and below. It’s a useful benchmark: equipment that meets that bar is engineered for exactly the conditions an Ontario winter produces, not just mild shoulder-season weather.

Why COP drops as it gets colder (and why that’s normal)

It’s true that a heat pump’s COP falls as the outdoor temperature drops — there’s simply less ambient heat to gather when it’s colder. That’s physics, and any honest installer will tell you so. The point isn’t that COP stays high forever; it’s that a well-designed cold-climate unit keeps COP above 1 — and usually well above it — across the entire range of temperatures Ontario experiences. You’re still ahead of resistance electric heat at every point on that curve.

Sizing is everything

Here’s the catch that separates a happy heat pump owner from a frustrated one: sizing. A heat pump must be matched to your home’s actual heat-loss profile, not simply swapped in at the same tonnage as your old furnace. Undersize it and it struggles on the coldest nights; oversize it and you waste money and short-cycle the system. That’s why we run a real load calculation on every install — see our explainer on why correct sizing matters more than size.

Heat pump or AC?

If you’re already replacing your air conditioner, it’s worth asking whether a heat pump makes more sense, since it both heats and cools. Our guide on when you should upgrade your air conditioner covers that decision, and our installation cost guide gives you real pricing.

Built for Canadian winters

We install cold-climate heat pumps across the GTA — engineered for the deep cold and sized to your specific home, not your old furnace’s nameplate. If you’ve been told a heat pump can’t handle Ontario, let us show you the data and the right unit for your house. Book a free quote and we’ll give you an honest assessment, usually within the hour.