How Does a Heat Pump Work in Winter?
- ryan comeau
- Jan 15
- 5 min read
Updated: 1 day ago
A heat pump works in winter by drawing heat from the outdoor air, even when it's cold, and moving it indoors through a refrigerant cycle. It doesn't burn fuel to create heat as a furnace does. It simply relocates heat that's already there, which is why a well-matched system keeps running efficiently through a Nova Scotia winter.
As a Mitsubishi Electric dealer who works on heat pumps across the HRM every day, I get some version of this question on almost every winter call: how does a heat pump work in winter when it's this cold outside? Here's the straightforward answer and why they’re worth it in Canada.
How Does a Heat Pump Work in Winter?
It pulls heat from outdoor air, even when it's cold, using the same basic principle as your refrigerator, just in reverse.
Cold outdoor air still contains usable heat energy, even at sub-zero temperatures. The outdoor unit's refrigerant absorbs this energy, and a compressor squeezes that refrigerant to raise its temperature. The now-hot refrigerant travels inside, where a fan blows air across it to release heat into your home.
The heat pump isn't generating warmth from nothing. It's extracting and concentrating heat that's already present in the outside air, which is a far more efficient way to heat a home than burning oil or propane.
The Heat Pump Heating Cycle: Step by Step
Absorb Heat Outdoors: The outdoor coil pulls heat from the surrounding air into the refrigerant.
Compress and Heat: The compressor pressurizes the refrigerant, raising its temperature significantly.
Release Heat Indoors: The indoor unit blows air across the hot coil, warming the air in your home.
Reset and Repeat: The refrigerant cools, returns outside, and restarts the cycle as long as your thermostat calls for heat.
Do Heat Pumps Work in Cold Climates Like Nova Scotia?
Yes, older heat pump models are why some homeowners still doubt it. Older models lost a lot of capacity below freezing, which is where the outdated reputation came from. Today's cold-climate models are a different product entirely.
Natural Resources Canada tested a cold-climate air-source heat pump at its Canadian Center for Housing Technology, and the results back this up:
Maintained a coefficient of performance above 1.5 at outdoor temperatures below -21°C
Still pulled more heat energy from the air than the electricity it consumed
Uses the same underlying technology found in the cold-climate Mitsubishi systems installed across Upper Sackville and the rest of the HRM
Adoption backs this up too. Manufacturers shipped more heat pumps than gas furnaces across North America in 2025, and unit sales are growing at a similar pace across Europe's coldest countries. Homeowners in genuinely cold climates aren't switching to a system that can't handle winter.
What's the Lowest Temperature a Heat Pump Will Work?
Older, standard heat pumps typically lose capacity around 4°C, struggle to keep up once temperatures drop toward -15°C, and need a backup heat source from that point on.
Cold-Climate Models Go Much Lower
Mitsubishi Hyper-Heat systems maintain full heating capacity down to -15°C. NRCan field testing showed cold-climate units operating down to roughly -28°C with backup support.
Halifax rarely sees sustained temperatures anywhere near that range, so a properly sized cold-climate heat pump can carry the full heating load on its own.
Sizing is where things go wrong. A heat pump that's undersized for your home will run harder than it should during a cold spell, which is often mistaken for a heat pump "not working in winter." A correctly sized, cold-climate-rated system won't have that problem.
Can I Use a Heat Pump With a Furnace?
Yes, hybrid systems are common in Halifax homes. The heat pump handles most of the winter heating load, and a furnace or electric backup kicks in only during extreme cold or a system fault. This works well for older homes with existing ductwork, or for homeowners who want a backup in place even when a properly sized cold-climate heat pump could manage on its own.
If you're weighing a full heat pump switch against a hybrid setup, it's worth a conversation about your specific home before deciding.
Does a Heat Pump Run All the Time in Winter?
Yes, and that's normal, not a malfunction. On the coldest days, a heat pump runs longer at a lower, steadier output rather than blasting hot air and shutting off like a furnace does. This is more efficient than a furnace's on-off cycle and keeps your home at a more even temperature.
If your system runs constantly and your home still feels cold, that's worth a look; it could mean your heat pump isn't heating well, or you're running into one of the more common winter heat pump issues.
Signs Your Heat Pump Needs a Professional Look This Winter
Reduced Airflow or Weak Heat: The unit runs, but the air doesn't feel as warm as usual. This often points to a refrigerant, filter, or coil issue rather than the technology itself.
Ice Buildup Beyond Normal Frost: A thin layer of frost that clears during defrost cycles is normal. Thick, persistent ice usually means the defrost cycle isn't working properly.
Rising Electric Bills Without Rising Comfort: If your bill is climbing but your home isn't any warmer, the system may be working harder to compensate for a mechanical problem. See why your electric bill is high with a heat pump.
Short Cycling: The unit turns on and off frequently instead of running in steady, longer cycles. This is often a sizing or component issue worth checking before it gets colder.
Getting your system looked at before the deep cold hits is easier than dealing with a breakdown mid-January.
Why Halifax Homeowners Trust Colgrove Air for Heat Pump Service
Most companies only work on the brands they sell. Colgrove Air services all heat pump brands, so you're not stuck if your system was installed by someone else. There's no call center or runaround; you speak with Ryan, the technician who shows up at your door, from the first call to the finished job.
Colgrove Air is an HVAC contractor in Upper Sackville, serving the entire Halifax Regional Municipality as an authorized Mitsubishi Electric dealer, and also servicing Gree and Tempstar systems. Consultations are free and no-pressure, focused on the right fit for your home rather than a sales pitch, and yes, we actually answer our phone, something that shouldn't be a differentiator, but often is in this industry.
Keep Your Halifax Home Warm All Winter
A heat pump works in winter by extracting heat from outdoor air and moving it inside through a refrigerant cycle, and modern cold-climate models are built to keep doing that through real Nova Scotia winters. The technology isn't the weak point; proper sizing, installation, and maintenance determine whether your system performs as it's supposed to.
If your heat pump isn't keeping up this winter, or you're not sure whether your current system is a cold-climate model, call us at (902) 830-1676 or book a free consultation. We'll give you a straight answer about what's going on with your system.
FAQs About Heat Pumps Working in Winter
Does a heat pump work when it's really cold outside?
Yes, cold-climate heat pumps are designed to keep producing heat well below -15°C, and they keep working even when it's really cold.
What is the lowest temperature a heat pump will work?
Standard models lose capacity around -15°C, but cold-climate systems like Mitsubishi Hyper-Heat continue operating down to roughly -28°C.
Can I use a heat pump with a furnace?
Yes, a hybrid heat pump and furnace setup is common in Halifax homes and works well for older houses with existing ductwork.
Should my heat pump run constantly in winter?
Yes, steady, longer run times at lower output are normal and more efficient than a furnace's on-off cycle.
Comments