It is the most common question we get about heat pumps: “Will it really keep my house warm when it is 5 below?”
The short answer is yes, if you choose the right kind of heat pump, size it correctly, and plan for the coldest few days of the year. The long answer is more useful, because “does it work” really means three different things: Will it keep up? How efficient is it in the cold? And what happens when Denver has one of its brutal arctic cold snaps?
This guide answers all three with real numbers, not sales talk.
Quick answer. Yes. A modern cold-climate heat pump can heat a Denver home through most of the winter. Denver’s average January low is around 17°F, and cold-climate models still heat efficiently well below that. To earn the ENERGY STAR Cold Climate label, a heat pump must still deliver at least 70 percent of its heating capacity at 5°F and use far less electricity than electric resistance heat at that temperature.
The catch is the rare arctic outbreak. Denver dropped to -19°F in January 2024. At those temperatures a heat pump’s output falls, so most Denver homes need a backup: either electric heat strips or a gas furnace (a “dual-fuel” system). Sized and set up correctly, a heat pump carries most of the load, and the backup covers the few coldest hours.
How a heat pump heats when it is freezing outside
A heat pump does not burn fuel to make heat. It moves heat from outdoor air into your home, the same way your refrigerator moves heat out of the food compartment.
Even very cold air holds heat. Air at 0°F still contains a lot of heat energy compared with the extremely cold refrigerant inside the outdoor coil. The heat pump’s refrigerant absorbs that heat outside, the compressor squeezes it to a higher temperature, and the indoor coil releases it into your ducts.
As the outdoor air gets colder, there is less heat to grab and the compressor has to work harder. That is why two things drop as temperatures fall:
- Capacity: how much heat the heat pump can deliver per hour
- Efficiency: how much heat you get for each unit of electricity
Older heat pumps struggled badly in the cold. Modern cold-climate heat pumps use variable-speed (“inverter”) compressors and improved refrigerant systems that keep both capacity and efficiency much higher at low temperatures.
What “efficient” means for a heat pump: COP
Heat pump efficiency at a given temperature is measured by the coefficient of performance (COP). COP is the amount of heat delivered divided by the electricity used.
- COP of 1 is the same as electric baseboard heat or electric heat strips. One unit of electricity makes one unit of heat.
- COP of 2 is twice as much heat as electric resistance for the same electricity.
- COP of 3 or more is three times as much heat.
A gas furnace does not have a COP. It is rated by AFUE, which is how much of the gas energy becomes heat (for example, 96 percent).
Heat pump performance at Denver temperatures
Here is how a good cold-climate heat pump typically performs across the range of temperatures Denver actually sees. Exact numbers vary by model, so always check the published data for the specific system you are considering.
| Outdoor temperature | What it means in Denver | Typical cold-climate heat pump performance |
|---|---|---|
| 47°F | A normal winter afternoon | Full rated capacity. Very efficient, often a COP around 3 to 4 |
| 17°F | About Denver’s average January low | Strong output from a good cold-climate model, still roughly 2 to 3 times more efficient than electric resistance |
| 5°F | A cold Denver night | ENERGY STAR Cold Climate models must still deliver at least 70 percent of their 47°F capacity, with a COP of at least 1.75 |
| Below 0°F | Arctic cold snaps, a few days in a typical winter | Output keeps dropping. Many cold-climate models keep running to around -13°F, some lower, but backup heat usually helps here |
The ENERGY STAR cold-climate requirements are published in the ENERGY STAR heat pump specification.
What this means: Even at 5°F, a qualifying cold-climate heat pump produces at least 75 percent more heat per unit of electricity than electric resistance heat. It still works; it just cannot always produce enough heat on its own for a whole house on the very coldest nights.
How cold does Denver actually get?
This is where Denver’s climate works in your favor more than people expect.
- Typical January. Normal highs are in the low to mid 40s and normal lows are around 17°F, according to National Weather Service Denver/Boulder climate data.
- Below-zero nights are rare but real. Historically, Denver averages only a couple of January nights at or below zero.
- Cold snaps can be severe. Denver International Airport hit -19°F on January 15 and 16, 2024, per the NWS 2024 climate summary. Denver also dropped below -20°F in December 2022.
- Sunny days rebound fast. Even in mid-winter, Denver often has sunny afternoons in the 40s and 50s. Heat pumps are at their most efficient on exactly those days.
So the design question for a Denver home is not “Can a heat pump handle winter?” It is “How do we cover the few coldest hours of the year?”
Denver-specific factors most articles skip
1. Altitude reduces heat pump capacity
At 5,280 feet, the air is roughly 15 to 17 percent less dense than at sea level. Thinner air carries less heat across the outdoor and indoor coils. This affects heat pumps the same way it affects air conditioners. We explain the effect in how Denver’s altitude affects your AC’s cooling capacity.
What it means for you: A heat pump sized from a sea-level rule of thumb may come up short here. Proper sizing uses a load calculation for your actual home and accounts for altitude.
2. Denver’s dry air means less frost
When outdoor air is cold and humid, frost builds on the outdoor coil. The heat pump then runs a short defrost cycle to melt it. Defrost uses energy and briefly reduces heat output.
Denver’s air is usually dry, so frost tends to build more slowly than in humid cold climates. You will still see defrost cycles, especially during snowy or foggy weather, but dry air is an advantage.
What defrost looks like: The outdoor fan stops, you may hear a whoosh, and you may see steam rising from the unit for a few minutes. That is normal.
3. Snow and ice around the outdoor unit
Heat pumps drain water when they defrost. In Denver, that water can refreeze at the base of the unit. Good installations:
- Mount the outdoor unit on a raised stand or wall bracket above typical snow depth
- Keep it out from under roof edges where snow and ice drip or slide
- Leave room for defrost water to drain away without forming an ice dam under the unit
4. Electricity pricing matters
Xcel Energy’s residential time-of-use rates charge the most from 5 p.m. to 9 p.m. on weekdays, all year, including winter. That is exactly when many families turn up the heat after work. A smart thermostat that warms the house a little before 5 p.m. can help. Xcel publishes the windows on its time-of-use pricing page.
Backup heat: the key decision for a Denver heat pump
Because output drops on the coldest nights, most Denver heat pump systems include a backup heat source. There are two main options.
| Electric heat strips | Gas furnace backup (dual fuel) | |
|---|---|---|
| How it works | Electric coils in the indoor air handler add heat when the heat pump cannot keep up | The heat pump heats most of the time; the gas furnace takes over below a set outdoor temperature |
| Best for | Homes without gas, or all-electric goals | Homes that already have gas and ducts, or want full capacity in any cold snap |
| Pros | Lower installed cost, no combustion, simple | Full heating power at any temperature, keeps heating if the heat pump needs repair |
| Cons | Expensive to run (COP of 1), and running strips during the 5 to 9 p.m. peak costs the most | Higher installed cost, still need gas service and furnace maintenance |
What is the “balance point”?
The balance point is the outdoor temperature where your heat pump’s output exactly matches your home’s heat loss. Above it, the heat pump handles everything. Below it, backup heat helps.
- For a well-sized cold-climate heat pump in a reasonably insulated Denver home, the balance point is often low enough that backup runs only during the coldest nights of the year.
- For a standard (non-cold-climate) heat pump, the balance point is much higher, and backup can run often. That is the main reason some Denver homeowners had bad experiences with older heat pumps.
With a dual-fuel system, the switch temperature can also be set by cost. When gas becomes cheaper per unit of heat than electricity at a given outdoor temperature, the furnace takes over. We compare the two fuels more broadly in gas furnace vs. heat pump in Denver.
What makes a heat pump work well (or badly) in Denver
In our experience, when a heat pump disappoints in Denver, the equipment is rarely the problem. The setup is. Here is what matters most.
1. Buy a true cold-climate model
Look for the ENERGY STAR Cold Climate label or published performance data at 5°F. Do not assume “high-efficiency” means “cold-climate.” Many standard heat pumps are very efficient in mild weather but weak in the cold.
2. Size it with a real load calculation
The installer should do a Manual J load calculation for your home, using Denver’s winter design temperature and altitude. They should then check the heat pump’s published capacity at low temperatures, not just its nameplate size.
A heat pump sized only for air conditioning will often be too small for Denver winter heating. Sized too large, it may short-cycle in mild weather. A variable-speed cold-climate unit handles this range best.
3. Fix duct problems first
Heat pump air is warm (often 85°F to 100°F at the vents), not hot like furnace air. That makes duct leaks and poorly placed registers more noticeable. Leaky or dirty ducts in attics, crawlspaces, or garages can make a heat pump feel weak even when it is working correctly. See our guide to how dirty ducts hurt efficiency.
4. Improve the “envelope” if you can
Every bit of heat loss you prevent lowers the balance point. Attic insulation and air sealing are often the cheapest way to make a heat pump carry more of the winter by itself. Xcel Energy offers insulation and air sealing rebates for eligible customers.
5. Set up the thermostat correctly
- Use a thermostat designed for heat pumps, set up for your specific system.
- Avoid big nighttime setbacks. Turning the heat down 8 degrees overnight and back up in the morning can force backup heat to kick in during recovery. Small setbacks of 2 to 3 degrees, or none at all, usually work better.
- Set the backup heat lockout temperature so strips or the furnace do not run when the heat pump could do the job.
6. Keep up with maintenance
Heat pumps run in summer and winter, so they need service twice a year. A spring and fall visit keeps the refrigerant charge, coils, defrost controls, and backup heat working. See our heat pump services.
Honest downsides to know before you switch
A heat pump is a strong choice for many Denver homes, but it is not perfect for every home. Be aware of:
- Different “feel.” Heat pumps run longer at lower air temperatures. Most people like the steady comfort; a few miss the blast of hot furnace air.
- Power outages. A heat pump needs electricity. So does a gas furnace’s blower and controls, so neither works in an outage without a generator.
- Electrical capacity. Some older homes need an electrical panel upgrade, especially with heat strip backup.
- Upfront cost. Cold-climate systems cost more than a basic furnace and AC. Rebates narrow the gap, but they change often.
What about rebates?
Colorado incentives for heat pumps have been generous but have changed several times in 2025 and 2026. As of late September 2026:
- Xcel Energy has offered cold-climate heat pump rebates of $2,250 per heating ton (measured at 5°F) for eligible customers with Xcel gas service. That amount was scheduled to step down to about $1,500 per heating ton on October 1, 2026.
- Colorado’s state heat pump tax credit is $1,000 for air-source systems in 2026. It is claimed by a registered contractor, who must pass part of it to you as a discount on your invoice.
- The federal 25C tax credit ended December 31, 2025.
Amounts change, so always confirm before you sign. We keep the details updated in our 2026 HVAC rebates and tax credits guide, and we cover installation costs in heat pump installation in Denver.
Is a heat pump right for your Denver home?
A heat pump is often a great fit if:
- Your AC is near the end of its life and you need cooling anyway
- You want one system for heating and cooling
- Your home is reasonably insulated and your ducts are in decent shape
- You are open to dual fuel, or your home is well insulated enough for heat strips to rarely run
You may want to think harder if:
- Your home is large, drafty, or poorly insulated and you are not ready to improve that
- Your ducts are small or leaky and cannot be fixed during the project
- Your electrical panel is maxed out
If you are replacing both a furnace and an AC, read our guide to when you should replace your furnace before deciding. For homes without ducts, ductless systems are another option; see our ductless mini-split guide.
Get a straight answer for your home
Every home is different. The only way to know how a heat pump will perform in yours is a real load calculation and a look at your ducts, insulation, and electrical panel.
Comfy Cave Heating & Air installs and services cold-climate heat pumps, dual-fuel systems, and gas furnaces across Denver, Arvada, and the surrounding metro. We will tell you honestly which option fits your home, including when a furnace is still the better choice.
Call 303-645-4889 or explore our heat pump services to schedule an in-home estimate. Financing is available through our financing options.
Frequently asked questions
Do heat pumps work in Denver winters?
Yes. Modern cold-climate heat pumps heat efficiently at Denver’s typical winter temperatures, including nights in the teens and single digits. For rare arctic cold snaps below zero, most Denver systems include backup heat, either electric heat strips or a gas furnace in a dual-fuel setup.
At what temperature does a heat pump stop working?
It depends on the model. Standard heat pumps lose a lot of capacity below about 25 to 30 degrees Fahrenheit. Cold-climate heat pumps must still deliver at least 70 percent of their rated capacity at 5 degrees to earn the ENERGY STAR Cold Climate label, and many keep running to around minus 13 degrees or lower. They do not suddenly stop; their output gradually drops.
Do I need backup heat with a heat pump in Denver?
In most Denver homes, yes. Denver can drop well below zero during arctic outbreaks, like minus 19 degrees in January 2024. Backup heat, either electric strips or a gas furnace, covers those hours. A well-sized cold-climate heat pump means backup rarely runs.
Is a heat pump cheaper to run than a gas furnace in Denver?
It depends on electricity and gas prices, the heat pump’s efficiency, and how cold the winter is. Heat pumps are usually most cost-effective in mild and moderate weather. Dual-fuel systems let the furnace take over when gas is cheaper per unit of heat. A local contractor can estimate costs for your home using current Xcel rates.
Does altitude affect heat pump performance?
Yes. At Denver’s altitude, the air is roughly 15 to 17 percent less dense than at sea level, so heat pumps move less heat across their coils. A proper load calculation and equipment selection should account for altitude.
Why does my heat pump blow steam in winter?
That is the defrost cycle. In cold weather, frost builds up on the outdoor coil. The heat pump briefly reverses to melt it, and the melting frost gives off steam. It usually lasts a few minutes and is completely normal.
What is a dual-fuel heat pump system?
A dual-fuel system pairs an electric heat pump with a gas furnace. The heat pump handles heating and cooling most of the year. When outdoor temperatures drop below a set point, the gas furnace takes over. It is a popular choice in Denver because it combines heat pump efficiency with full gas heating power in cold snaps.
Can a heat pump replace my furnace completely in Denver?
In a well-insulated home with a properly sized cold-climate heat pump and electric backup strips, yes. Many Denver homeowners choose dual fuel instead, keeping a gas furnace for the coldest days. The right answer depends on your home’s heat loss, your ducts, and your electrical panel.
Find Out If a Heat Pump Fits Your Home
A real load calculation, a look at your ducts, insulation and panel, and an honest answer, including when a furnace is still the better choice.