Heat pumps move heat rather than generate it, so they use far less energy than furnaces or electric resistance heating

A heat pump's efficiency is measured by how much heating or cooling you get for every unit of electricity you put in. In ideal conditions—mild weather, well-insulated homes, newer equipment—a heat pump delivers 2 to 4 times as much heat energy as the electrical energy it consumes. A gas furnace, by contrast, converts fuel into heat at roughly 90 percent efficiency, meaning 90 percent of the fuel's energy becomes usable heat. That sounds close until you do the math: a heat pump pulling heat from outside air and moving it indoors can deliver the equivalent of 200 to 400 percent of the electrical energy it uses, because it is not burning anything—it is relocating what is already there.

The catch is that efficiency drops when outdoor temperatures fall. As the air gets colder, there is less heat available to move, and the heat pump must work harder to extract it. Below 32°F, most air-source heat pumps lose efficiency noticeably. Below 0°F, many models switch to electric resistance heating (essentially a space heater inside the unit), which burns energy at 100 percent efficiency—better than nothing, but far worse than the heat pump itself. Ground-source heat pumps, which pull heat from the earth rather than the air, stay efficient in cold weather because soil temperature stays relatively stable underground, but they cost significantly more to install.

Key Takeaways

  • Heat pumps deliver 2 to 4 times as much heating energy as the electricity they consume in moderate weather, making them far more efficient than electric resistance heating or gas furnaces in most climates.
  • Efficiency drops sharply below 32°F and becomes poor below 0°F, when many air-source heat pumps switch to backup electric heating.
  • A heat pump's real-world performance depends on your home's insulation, the outdoor temperature range where you live, and how well the system is sized and installed.
  • Ground-source heat pumps maintain high efficiency year-round but cost two to three times more to install than air-source models.
  • Pairing an air-source heat pump with a gas furnace or boiler as backup can preserve efficiency in very cold climates while avoiding the cost of ground-source installation.

How the efficiency rating system works

Heat pump efficiency is reported as HSPF (Heating Seasonal Performance Factor) for heating and SEER2 (Seasonal Energy Efficiency Ratio) for cooling. HSPF is the number you will see most often when shopping. An HSPF of 8 means the system delivers 8 units of heat for every 1 unit of electricity consumed, averaged across a typical heating season. Older units might be HSPF 6 or 7. Newer, high-efficiency models reach HSPF 10 or higher.

These ratings are measured in a laboratory under standard conditions, not in your actual home during a January cold snap. The "seasonal" part of the rating accounts for the fact that efficiency varies month to month, but it assumes an average winter for a moderate climate. If you live somewhere that regularly drops below 0°F, your real-world efficiency will be lower than the HSPF number suggests. If you live in a mild climate where winter temperatures rarely fall below 40°F, your actual efficiency may exceed the rating.

Why efficiency matters less in mild climates

In regions where winter temperatures stay above 40°F most of the time—the Pacific Northwest, much of the South, coastal California—a heat pump operates near its peak efficiency for most of the heating season. In these climates, switching from a gas furnace to a heat pump can cut heating energy use by 50 percent or more. The system rarely needs backup heating, and the electricity it uses is often cheaper per BTU than the gas it would replace.

Mild-climate homeowners also benefit from the cooling side. A heat pump that heats efficiently in winter also cools efficiently in summer, so you get one system doing both jobs. A gas furnace requires a separate air conditioner, which means higher upfront cost and more equipment to maintain.

Why efficiency drops in cold climates

Below 32°F, the outdoor coil of an air-source heat pump begins to frost over. The system must periodically reverse itself to defrost the coil, which temporarily stops heating your home and uses energy to warm the coil instead. This defrost cycle happens more often as temperatures fall, eating into overall efficiency.

Below 0°F, most air-source heat pumps are designed to switch to electric resistance heating automatically. This is a safety feature—the heat pump can still technically operate, but it becomes so inefficient that running it would waste energy. The backup heater takes over. In very cold climates, you might spend weeks running on backup heat, which means your efficiency advantage over a gas furnace shrinks or disappears entirely.

Some newer cold-climate heat pumps are engineered to stay efficient down to -13°F or lower, but they cost more upfront. If you live in a climate where temperatures regularly drop below 0°F, a cold-climate model or a hybrid system (heat pump plus gas furnace) usually makes more financial sense than a standard air-source heat pump.

Real-world efficiency depends on your home and installation

Two identical heat pumps in two identical homes can perform very differently if one home is poorly insulated and the other is well-sealed. A heat pump works by moving heat in and out; if your home leaks heat through gaps, poor windows, or thin walls, the heat pump must run longer and harder to maintain temperature. Insulation upgrades often pay for themselves faster than a new heat pump.

Installation quality also matters. A heat pump that is oversized for your home will cycle on and off frequently, reducing efficiency. One that is undersized will run constantly and never quite reach your target temperature. A may have access to installer will perform a heat load calculation to size the system correctly. Poor refrigerant charge, leaky ductwork, or a clogged filter can also cut efficiency by 10 to 20 percent.

Ground-source heat pumps stay efficient in any climate

A ground-source heat pump (also called a geothermal heat pump) pulls heat from the earth via underground pipes, where temperature stays between 45°F and 55°F year-round in most of North America. Because the heat source is always warm relative to winter air, the system maintains high efficiency even in the coldest climates. HSPF ratings for ground-source systems often reach 10 to 12, and they do not degrade in winter.

The trade-off is cost. Ground-source installation requires drilling or trenching to bury the heat exchanger loop, which can cost $15,000 to $30,000 or more depending on soil conditions and loop design. For most homeowners, this is only worth it if you are replacing an old heating system anyway and plan to stay in the home for at least 10 years. In mild climates, an air-source heat pump usually makes more financial sense.

Hybrid systems: heat pump plus gas furnace

A hybrid system pairs an air-source heat pump with a gas furnace or boiler. The heat pump runs whenever outdoor temperature is above its efficiency threshold (usually around 35°F to 40°F). Below that, the gas furnace takes over. This approach keeps you in the efficient heat pump zone for most of the season while avoiding the cost of a cold-climate heat pump or ground-source system.

Hybrid systems work well in climates with cold winters but not extreme cold—places where temperatures drop below freezing regularly but rarely stay below 0°F for weeks. The heat pump handles the bulk of the heating load, cutting energy use compared to a furnace alone, while the furnace provides reliable backup without the efficiency penalty of electric resistance heating. The downside is maintaining two heating systems instead of one.

How to compare heat pump efficiency to your current system

If you heat with electricity (baseboard heaters, electric furnace, or resistance heating), a heat pump with an HSPF of 8 or higher will cut your heating costs by at least 50 percent, even in cold climates. The math is straightforward: you are replacing a system that converts 1 unit of electricity into 1 unit of heat with one that converts 1 unit of electricity into 8 units of heat.

If you heat with gas, the comparison is more complex because gas is often cheaper per BTU than electricity in your area. A heat pump makes the most financial sense if your electricity rate is low, your winters are mild, or you plan to stay in your home long enough to recoup the upfront cost through energy savings. Your local utility may offer a rebate for switching to a heat pump, which can shorten the payback period significantly.

Frequently Asked Questions

Will a heat pump work in my climate if it gets below zero?

Standard air-source heat pumps switch to electric backup heating below 0°F, so efficiency drops sharply. Cold-climate heat pumps stay efficient down to -13°F or lower but cost more. In very cold regions, a hybrid system (heat pump plus gas furnace) or ground-source heat pump is usually more practical.

Does a heat pump lose efficiency as it gets older?

Yes, gradually. Refrigerant leaks, compressor wear, and coil fouling reduce efficiency over time. A well-maintained heat pump should lose only 1 to 2 percent of efficiency per decade. Regular filter changes and professional servicing every 1 to 2 years help preserve performance.

Can I improve my heat pump's efficiency after installation?

Yes. Sealing air leaks, adding insulation, upgrading windows, and cleaning or replacing filters all reduce the load the heat pump must handle. These improvements often cost less than replacing the system and can improve efficiency by 10 to 20 percent.

What is the difference between HSPF and SEER2?

HSPF measures heating efficiency; SEER2 measures cooling efficiency. A heat pump has both ratings. HSPF tells you how much heat you get per unit of electricity in winter; SEER2 tells you how much cooling you get per unit of electricity in summer.

Is a heat pump more efficient than a high-efficiency gas furnace?

In most climates, yes. A 95 percent efficient gas furnace converts 95 percent of fuel into heat. A heat pump with HSPF 8 delivers 8 times as much heat energy as the electricity it uses. The heat pump wins unless your electricity is much more expensive than gas in your area.