Heat Pump COP vs Temperature Chart
This is the core of the article — the master COP-by-temperature reference.
The chart above plots COP on the Y-axis (1.0 to 5.0) against outdoor temperature on the X-axis (-20°F to 60°F). Four lines are shown: a standard air-source heat pump, a cold-climate heat pump (ccASHP), a gas furnace equivalent (~0.95 COP), and electric resistance heat (COP 1.0). The horizontal reference line at COP 1.0 marks the break-even point with electric resistance.
Here's the data behind those curves:
Master COP by Temperature Table
| Outdoor Temp | Standard Heat Pump (COP) | Cold Climate Heat Pump (COP) | Gas Furnace Equivalent (COP) | Electric Resistance (COP) |
|---|
| 60°F | 4.0–4.5 | 4.2–4.8 | 0.80–0.96 | 1.0 |
| 47°F (AHRI rated) | 3.5–4.0 | 3.8–4.5 | 0.80–0.96 | 1.0 |
| 35°F | 2.8–3.2 | 3.0–3.5 | 0.80–0.96 | 1.0 |
| 30°F | 2.5–2.9 | 2.8–3.2 | 0.80–0.96 | 1.0 |
| 17°F (AHRI low-temp) | 1.7–2.4 | 2.2–3.0 | 0.80–0.96 | 1.0 |
| 5°F | 1.0–1.8 | 1.8–2.6 | 0.80–0.96 | 1.0 |
| -5°F | Lockout or <1.5 | 1.5–2.2 | 0.80–0.96 | 1.0 |
| -15°F | Lockout | 1.2–1.8 | 0.80–0.96 | 1.0 |
Sources: NREL/TP-5500-84745 field data, PNNL-37127 DOE CCHP Challenge field validation (22 sites), NEEP ccASHP Product List database, manufacturer expanded performance tables.
The takeaway is clear. Even at 5°F, a cold-climate heat pump with a COP of 2.0 is still twice as efficient as electric resistance heat. And it doesn't hit the gas furnace "break-even" point until well below freezing — if it hits it at all, depending on your local energy prices.
The Coefficient of Performance, or COP, is the simplest measure of heat pump efficiency. It tells you how much heat you're getting per unit of electricity consumed.
COP = Heat Output (BTU or kWh) ÷ Electrical Input (BTU or kWh)
A COP of 1.0 means you're getting exactly as much heat as the electricity you're putting in — that's what electric resistance heat does. A COP of 3.0 means you're getting 3x the heat output for the same electricity. That's where heat pumps shine.
Here's the deal: COP is a snapshot at a specific moment — specific outdoor temperature, indoor temperature, and compressor speed. It's not a seasonal average.
For seasonal performance, we use HSPF (Heating Seasonal Performance Factor), which is essentially a weighted average of COP across an entire heating season. You can learn more about how HSPF ratings work and how they relate to COP.
To convert between the two: Seasonal COP ≈ HSPF ÷ 3.412. An HSPF of 10 translates to roughly a seasonal COP of 2.93. For cooling efficiency, a parallel metric — SEER rating — measures performance across a cooling season. When sizing a heat pump for both heating and cooling, you'll also want to verify the cooling side with our AC tonnage calculator.
If you want to calculate COP for a specific set of conditions, use our COP calculator.
Not all heat pumps are built for cold weather. The difference between a standard unit and a cold-climate unit is dramatic below 30°F.
A standard air-source heat pump uses a fixed-speed or basic inverter compressor. As outdoor temperatures drop, the available heat in outdoor air decreases, the refrigerant pressure drops, and the compressor has to work much harder. By 17°F, a standard unit typically delivers only 60–70% of its rated capacity.
A cold-climate heat pump (ccASHP) fights back with three key technologies: variable-speed inverter compressors that ramp up as demand increases, Enhanced Vapor Injection (EVI) that injects extra refrigerant mid-compression for higher capacity, and oversized outdoor coils that pull more heat from cold air. The result is dramatically better capacity retention.
Heating Capacity at Low Temperatures: Standard vs Cold Climate
| Outdoor Temp | Standard HP (% of 47°F Capacity) | Cold Climate HP (% of 47°F Capacity) |
|---|
| 47°F | 100% | 100% |
| 35°F | 85–90% | 90–95% |
| 17°F | 60–70% | 75–85% |
| 5°F | 40–55% | 75–100% |
| -5°F | 25–35% (if running) | 60–80% |
| -13°F | Lockout | 50–75% |
Sources: NEEP ccASHP Specification V4.0, AHRI 210/240 rated data, manufacturer expanded performance tables.
That capacity retention matters enormously for heat pump sizing. If your heat pump loses 50% of its capacity at your design temperature, you'll need supplemental electric resistance strips — which operate at COP 1.0 — dragging your overall system efficiency down hard.
Cold Climate Heat Pump Model Comparison: Real BTU Output and COP at 5°F
| Model | Type | Rated Cap @ 47°F | Cap @ 5°F | COP @ 5°F | Min Operating Temp | Refrigerant |
|---|
| Mitsubishi MUZ-FH24NA (Hyper-Heat) | Ductless | 30,600 BTU/h | 27,400 BTU/h | 2.4 | -13°F | R-32 |
| Daikin Aurora RXP24AVJU9 | Ductless | 27,600 BTU/h | ~24,000 BTU/h (100%) | ~2.0 | -13°F | R-32 |
| Bosch IDS Ultra | Ducted | Up to 60,000 BTU/h | 100% rated | 2.1 | -13°F | R-454B |
| Carrier Infinity CCHP | Ducted | Varies by size | 100% rated at 0°F | >2.0 | -23°F | Low-GWP |
| Fujitsu XLTH | Ductless | Varies | ~70–80% rated | ~2.0–2.25 | -15°F | R-410A |
Sources: Mitsubishi spec sheets (100% capacity at 5°F, 75% at -13°F), Bosch IDS Ultra (DOE CCHP Challenge certified, COP 2.1 at 5°F), Daikin product specs (100% capacity at 5°F), Carrier DOE Challenge results (100% capacity at 0°F, operates to -23°F), NEEP product database (ashp.neep.org).
The Carrier Infinity is worth noting — it's the highest-rated DOE Cold Climate Heat Pump Challenge unit, delivering 100% capacity at 0°F and operating all the way down to -23°F. That's the new frontier for residential heat pumps.
You can look up these models and compare others on the NEEP Cold Climate Air Source Heat Pump Product List.
How Do Cold Climate Heat Pumps Maintain Efficiency Below Freezing?
Three technologies make the difference:
- Enhanced Vapor Injection (EVI): The compressor injects flash-vaporized refrigerant mid-compression. This increases refrigerant mass flow at low outdoor temps, boosting both capacity and COP. Bosch, Carrier, and others use EVI compressors in their cold-climate lines.
- Variable-speed inverter compressors: Instead of cycling on/off, these compressors modulate continuously from minimum to maximum output. This lets the unit ramp up to full power in extreme cold and run at efficient low speeds in mild weather — a principle that applies equally to mini-split systems.
- Advanced refrigerants: Newer R-32 (Mitsubishi, Daikin) and R-454B (Bosch) refrigerants have better thermodynamic properties at low temperatures than legacy R-410A. The way refrigerant pressure and temperature interact is what ultimately drives COP changes across the temperature range.
The result? A modern ccASHP on the NEEP list must deliver a COP of at least 1.75 at 5°F at max capacity, per the ccASHP V4.0 specification. Many models exceed that threshold significantly.
At What Temperature Does a Heat Pump Become Inefficient?
This is one of the most searched questions in the heat pump space — and the answer depends entirely on what you mean by "inefficient."
If "inefficient" means COP drops below 1.0 (worse than electric resistance), most modern heat pumps never reach that point during normal operation. Even at -15°F, cold-climate units maintain COPs of 1.2–1.8. You're still getting more heat than the electricity you're putting in.
If "inefficient" means more expensive than gas, that depends on your local electricity and gas prices. We'll cover that exact calculation in the economic crossover section below.
What Temperature Does a Heat Pump Stop Working?
A standard heat pump typically has a compressor lockout somewhere between 0°F and 25°F, depending on the model and controls. Below this temperature, the unit shuts down completely, and electric resistance backup takes over.
A cold-climate heat pump is a completely different story. Here are the minimum operating temperatures for major ccASHP models:
| Model | Minimum Operating Temperature |
|---|
| Carrier Infinity CCHP | -23°F |
| Fujitsu XLTH | -15°F |
| Mitsubishi Hyper-Heat | -13°F |
| Daikin Aurora | -13°F |
| Bosch IDS Ultra | -13°F |
The key distinction: "minimum operating temperature" is not the same as "efficient operating temperature." The unit will still run at -13°F, but its COP may have dropped to 1.5 or below. That's still 50% better than electric resistance — but it's a far cry from the COP 4.0+ you enjoy at 47°F.
For a deep dive on the full heat pump temperature range, including both heating and cooling limits, check our dedicated article.
Balance Point: When Your Heat Pump Needs Backup Heat
The balance point is the outdoor temperature where your heat pump's maximum heating capacity exactly equals your home's heat loss. Below this point, the heat pump alone can't keep up.
Think of it like two lines on a graph. Your home's heat loss increases as outdoor temperature drops (it's a straight line). Your heat pump's capacity decreases as outdoor temperature drops (it's a curve).
Where they cross? That's the balance point.
How to Calculate Your Heat Pump Balance Point
Here's the methodology:
- Calculate your home's heat loss rate. You need a Manual J load calculation (or a simplified version). The formula is: Heat Loss (BTU/h) = Building UA × (Indoor Temp – Outdoor Temp). A typical well-insulated home has a UA of 300–500 BTU/h per °F of temperature difference. A poorly insulated home might be 600–900 BTU/h per °F.
- Get your heat pump's capacity at multiple temperatures. Pull from the manufacturer's expanded performance tables (available on NEEP at ashp.neep.org). You need capacity at least at 47°F, 17°F, and 5°F.
- Plot both on the same graph. The heat loss is a straight line sloping up to the left. The heat pump capacity is a curve sloping down to the left. Where they cross is your balance point.
For a well-insulated 2,000 sq ft home (UA ≈ 400 BTU/h/°F) with a properly sized 3-ton cold-climate heat pump, the balance point is typically 0°F to 10°F. That means the heat pump covers the entire heating load for most of the winter without supplemental heat.
For a poorly insulated 2,000 sq ft home (UA ≈ 700 BTU/h/°F) with a standard 3-ton heat pump, the balance point might be 25°F to 35°F — meaning you need backup heat for a significant chunk of the heating season.
Use our heating BTU calculator to estimate your building's heat loss, and our heat pump sizing guide to match it against equipment capacity.
Heat Pump vs Gas Furnace: The Economic Crossover Point
Here's the question homeowners with dual-fuel systems really want answered: at what outdoor temperature should I switch from the heat pump to the gas furnace?
The answer isn't a fixed temperature — it's whatever temperature corresponds to the break-even COP for your local energy prices.
Break-Even COP = (Electricity Price per kWh ÷ Gas Price per Therm) × 29.3 ÷ Furnace AFUE
When your heat pump's actual COP drops below this number, gas is cheaper to run. When it's above, the heat pump is cheaper.
Economic Crossover Point: Heat Pump vs Gas at Various Energy Prices
| Electricity ($/kWh) | Gas ($/therm) | Furnace AFUE | Break-Even COP | Approx. Crossover Temp |
|---|
| $0.10/kWh | $1.50/therm | 95% | 2.0 | ~0–5°F (HP wins almost always) |
| $0.12/kWh | $1.50/therm | 95% | 2.5 | ~15–20°F |
| $0.12/kWh | $1.00/therm | 95% | 3.7 | ~40–45°F |
| $0.14/kWh | $1.10/therm | 95% | 3.9 | ~42–47°F |
| $0.16/kWh | $1.20/therm | 95% | 4.1 | ~45°F+ (gas almost always cheaper) |
| $0.16/kWh | $1.46/therm | 80% | 4.0 | ~43–47°F |
Sources: ACCA Manual H methodology, Mitsubishi operating cost comparison methodology, UniColorado switchover calculator, PickHVAC break-even calculations.
The takeaway: if your electricity is cheap and gas is expensive, the heat pump wins across nearly all temperatures. If the ratio flips — cheap gas, expensive electricity — the crossover point moves to mild outdoor temperatures where the heat pump barely has a COP advantage.
For a full cost comparison, check our heat pump running cost guide and our gas vs electric heating comparison.
How Defrost Cycles Impact Heat Pump Efficiency
When outdoor temperatures are between 20°F and 40°F and humidity is high, frost builds up on the outdoor coil. Your heat pump periodically reverses into cooling mode for 2–10 minutes to melt this frost. During defrost, it's not heating your home — and if electric resistance backup strips kick on, efficiency takes a hit.
Here's what the research shows:
| Impact | Data |
|---|
| Seasonal efficiency penalty (demand defrost) | ~7–10% reduction in seasonal COP |
| Seasonal efficiency penalty (time-based defrost) | ~10–16% reduction in seasonal COP |
| Capacity during defrost | 0% (heat pump is in cooling mode) |
| Defrost cycle frequency | 3–5 cycles/day in frost-prone conditions |
| Defrost duration | 2–10 minutes per cycle |
| Worst-case mal-defrost | Up to 40% COP drop, 43% capacity drop |
Sources: Purdue University IRACC Paper 1898 (Martin et al., 2018): 10–15% seasonal efficiency reduction. Klingebiel et al. (2025, Energy journal): demand-based defrost limits losses to 7% vs optimal, time-based up to 16%. NREL/TP-5500-84745: defrost energy exceeded 20% of compressor heating at 4 of 12 sites.
Modern cold-climate units use demand defrost — they defrost only when sensors detect actual frost buildup, rather than on a fixed timer. This alone can save 5–9% of seasonal efficiency compared to outdated time-based defrost controls.
Auxiliary Heat vs Emergency Heat: What's the Difference?
This comes up constantly and is directly related to efficiency at low temperatures. Let's clear it up.
Auxiliary heat ("AUX" on your thermostat) is your backup electric resistance heating strips. They kick on automatically when the heat pump can't meet demand alone — typically when outdoor temperatures drop below the balance point or during defrost cycles. The heat pump keeps running; the strips supplement it.
Emergency heat ("EM HEAT" on your thermostat) shuts the heat pump compressor OFF entirely and runs only the electric resistance strips. This is for emergencies — like when the compressor has failed. It's COP 1.0, so it's expensive.
| Feature | Auxiliary Heat ("AUX") | Emergency Heat ("EM HEAT") |
|---|
| Heat pump compressor | Running | OFF |
| Electric resistance strips | Running (supplemental) | Running (sole heat source) |
| When to use | Automatic — system decides | Manual — only if compressor fails |
| COP | Blended (>1.0, depends on HP contribution) | 1.0 (electric resistance only) |
| Cost | Higher than HP-only, lower than EM | Highest possible |
The bottom line: never manually switch to emergency heat unless your compressor is broken. You're paying 2–4x more for the same heat.
If your thermostat frequently shows "AUX," it may be a sign that your heat pump is undersized or that your balance point is set too high. Consider running a proper furnace sizing or heat pump sizing calculation.
Lab numbers are great. Field data is better. Here's what major government studies have actually measured:
NREL Field Study (2023): 12 Ducted Heat Pumps in Cold Climates
NREL monitored 12 centrally ducted, variable-speed heat pumps in homes across Washington, Montana, and Colorado over one or two full winters.
- Average seasonal compressor COP: 2.5 (range: 1.7 to 3.5)
- At sites where the heat pump was properly sized, 95%+ of heating load was met by the compressor alone
- Auxiliary electric resistance heat consumed >40% of compressor heating energy at 5 of 11 all-electric sites — primarily due to undersizing, control faults, and aggressive defrost settings
Source: Winkler & Ramaraj (2023). Field Validation of Air-Source Heat Pumps for Cold Climates. NREL/TP-5500-84745.
DOE Cold Climate Heat Pump Challenge (2022–2024): 22 Sites
The DOE partnered with 8 HVAC manufacturers (Bosch, Carrier, Daikin, Lennox, and others) to develop and field-test next-generation cold-climate heat pumps.
- Compressor-only heating COPs ranged from 1.8 at -15°F to 3.5 at 45°F
- CCHPs were reliable and provided heat with little assistance from auxiliary elements, even during the coldest winter periods
- Homeowner heating satisfaction increased from 3.61 to 3.88 (out of 5) after installation
Source: PNNL-37127 (2024). Performance Results from DOE Cold Climate Heat Pump Challenge Field Validation.
NREL Connecticut Field Test (2013): Seasonal COP 2.68–3.22
An earlier NREL study measured a low-temperature heat pump in Connecticut over two full winters.
- Year 1 seasonal COP: 3.22 | Year 2 seasonal COP: 2.68
- On the coldest day (average outdoor temp 15.8°F), the system achieved a daily COP of 2.4
Source: Johnson (2013). Measured Performance of a Low Temperature Air Source Heat Pump. NREL/TP-5500-56393.
These studies confirm: properly sized cold-climate heat pumps deliver real-world seasonal COPs of 2.5–3.2 across a full heating season, even in cold climates.
Worked Examples
Example 1: COP and Running Cost in a Mild Climate (Nashville, TN)
Let's say you have a 2,500 sq ft home in Nashville, Tennessee with a cold-climate heat pump. The design temperature is about 14°F (ASHRAE 99%), but the average January temperature is roughly 37°F.
At 37°F, your ccASHP is running at a COP of approximately 3.2. You need about 40,000 BTU/h of heating output.
- Electrical input = 40,000 BTU/h ÷ (3.2 × 3,412 BTU/kWh) = 3.66 kW
- At $0.12/kWh, that's $0.44/hour to heat your home
- Over a typical January day (heating ~16 hours): $7.04/day or ~$218/month
Example 2: COP and Running Cost in Extreme Cold (Minneapolis, MN)
Same home size, but now it's -5°F in Minneapolis. Your ccASHP COP drops to about 1.8. Your home needs about 70,000 BTU/h (more heat loss due to bigger ΔT).
- Electrical input = 70,000 ÷ (1.8 × 3,412) = 11.4 kW
- At $0.14/kWh, that's $1.60/hour
- Over a 24-hour cold snap: $38.40/day
Compare that to electric resistance (COP 1.0): 11.4 kW × 1.8 = 20.5 kW required, costing $2.87/hour or $68.88/day. The heat pump saves you $30/day even at -5°F.
Example 3: Balance Point Calculation
Your home has a calculated heat loss of 450 BTU/h per °F of temperature difference (from a Manual J calculation). Indoor setpoint is 70°F. Your 3-ton ccASHP delivers:
- 36,000 BTU/h at 47°F
- 30,000 BTU/h at 17°F
- 27,000 BTU/h at 5°F
At what outdoor temp does heat loss exceed capacity?
- Heat loss at 0°F: 450 × (70 – 0) = 31,500 BTU/h
- HP capacity at 0°F (interpolating): ~28,500 BTU/h
- Heat loss at 5°F: 450 × (70 – 5) = 29,250 BTU/h
- HP capacity at 5°F: 27,000 BTU/h
The balance point is approximately 7°F. Below that, supplemental heat kicks in.
In Nashville, you'd rarely need it. In Minneapolis, you'd need it maybe 200–400 hours per winter — less than 15% of the heating season.
Example 4: Economic Crossover — Should I Switch to Gas at 25°F?
You have a dual-fuel system. Electricity costs $0.13/kWh, gas costs $1.20/therm, and your furnace is 95% AFUE.
Break-even COP = (0.13 ÷ 1.20) × 29.3 ÷ 0.95 = 3.34
Your heat pump's COP at 25°F is approximately 2.7. Since 2.7 < 3.34, the gas furnace is cheaper at this temperature with these rates.
Your heat pump's COP at 40°F is approximately 3.5. Since 3.5 > 3.34, the heat pump is cheaper at this temperature.
So the optimal switchover point is somewhere around 35–38°F. Below that, let the furnace take over. Set your thermostat's balance point accordingly.
Example 5: Dual Fuel Crossover With Cheaper Electricity
Same setup, but your electricity is $0.09/kWh (common in Pacific Northwest) and gas is $1.40/therm.
Break-even COP = (0.09 ÷ 1.40) × 29.3 ÷ 0.95 = 1.98
Now the heat pump is cheaper to run at every temperature above roughly -5°F to 0°F. With cheap electricity, you'd almost never need to switch to gas. Keep the heat pump running.
FAQ: Heat Pump Efficiency and Temperature
At What Temperature Is a Heat Pump No Longer Efficient?
A heat pump is always more efficient than electric resistance heat, as long as its COP stays above 1.0. Modern cold-climate units maintain COP above 1.0 even at -13°F to -15°F.
The real question is whether it's cheaper than gas — that depends on your local energy prices, not just temperature. Use the break-even formula above to find your crossover point.
What Temperature Does a Heat Pump Stop Working?
Standard heat pumps may lock out between 0°F and 25°F. Cold-climate models operate to -13°F (Mitsubishi, Daikin, Bosch) or even -23°F (Carrier Infinity CCHP).
"Stop working" doesn't mean the compressor fails — it means the controls shut it down to protect the equipment. Learn more about the full heat pump temperature range.
Is Auxiliary Heat the Same as Emergency Heat?
No. Auxiliary heat supplements the heat pump automatically — both run at the same time. Emergency heat shuts the compressor OFF and runs only electric resistance strips.
Emergency heat costs 2–4x more. Never use it unless your compressor is actually broken.
Do Heat Pumps Work in Cold Climates?
Yes — if you select a cold-climate-rated model. Look for units on the NEEP ccASHP Product List that deliver COP ≥ 1.75 at 5°F. The DOE Cold Climate Heat Pump Challenge has validated that next-gen units provide reliable, efficient heating with minimal auxiliary heat even during the coldest winter periods.
What Is the Balance Point of a Heat Pump?
The balance point is the outdoor temperature where your heat pump's maximum capacity equals your home's heat loss. Below this temperature, supplemental heat is needed.
For a well-insulated home with a properly sized ccASHP, the balance point is typically 0°F to 15°F. For a poorly insulated home with a standard unit, it could be 25°F to 35°F.
Is a Heat Pump Cheaper to Run Than a Gas Furnace?
It depends on your local electricity and gas prices. Use this formula: Break-even COP = ($/kWh ÷ $/therm) × 29.3 ÷ AFUE.
If your heat pump's actual COP (at a given temperature) exceeds this number, the heat pump is cheaper. At national average rates (~$0.16/kWh electricity, ~$1.20/therm gas), the crossover COP is about 4.1 — meaning gas is often cheaper in cold weather.
But if your electricity is under $0.10/kWh, the heat pump wins at nearly all temperatures. Check our gas vs electric heating comparison for a deeper analysis.