Heat Pumps: Types, Sizing, Efficiency Ratings, and Cold-Climate Performance
FriendsWithTools.io earns a commission from qualifying purchases made through links on this page, at no additional cost to you. We do not test these tools ourselves — all claims are sourced from manufacturer specifications, retailer listings, and aggregated user reviews, each linked inline. Prices and ratings were verified on May 2026 and may have changed.
Heat pumps move heat rather than generating it, which makes them dramatically more efficient than furnaces and boilers. A well-matched heat pump delivers 2 to 4 times more heating energy than the electricity it consumes. They also cool in summer by running the refrigerant cycle in reverse, so one system replaces both your furnace and air conditioner. Modern cold-climate models work effectively well below zero degrees Fahrenheit, a significant improvement over the technology available even a decade ago.
How Heat Pumps Work
A heat pump uses a refrigerant cycle to absorb heat from one place and release it in another. In heating mode, it extracts heat from outdoor air (or the ground) and moves it inside. In cooling mode, it extracts heat from indoor air and dumps it outside. The compressor does the heavy lifting, pressurizing the refrigerant to raise its temperature on the discharge side and lowering it on the intake side.
This is the same technology as your refrigerator or window air conditioner. The only difference is that a heat pump can run the cycle in both directions. A conventional central AC unit is technically a one-way heat pump that only cools. Adding a reversing valve and some control logic turns it into a full heat pump that handles both heating and cooling.
The efficiency advantage comes from a simple physical principle: moving heat requires less energy than creating it. A 96% efficient gas furnace converts 96 cents of every dollar of natural gas into heat. That sounds good until you compare it to a heat pump with a coefficient of performance (COP) of 3, which delivers $3 of heat for every $1 of electricity. Even accounting for the higher cost of electricity per BTU compared to natural gas, the heat pump usually wins on operating cost in moderate climates and is competitive even in cold ones.
Air-Source Heat Pumps
Central air-source heat pumps look and install much like traditional AC condenser units. An outdoor unit connects to indoor ductwork via a refrigerant line set. If you are replacing an existing central AC and furnace, a ducted air-source heat pump uses the same ductwork and thermostat location. The outdoor unit is slightly larger than a conventional AC condenser but sits on the same concrete pad.
Performance drops as outdoor temperature decreases because there is less heat energy in colder air. Standard air-source heat pumps become inefficient below about 25 to 30 degrees Fahrenheit and need supplemental heat for the coldest days. That supplemental heat is typically electric resistance strips built into the air handler or a backup gas furnace. The resistance strips work but are expensive to run since they have a COP of 1.0 (no efficiency gain).
Cold-climate models have changed this equation substantially. The Mitsubishi Hyper-Heat, Fujitsu XLTH, Bosch IDS, and Daikin Fit maintain their rated heating capacity down to 5 degrees Fahrenheit and produce usable heat well below zero. These units use larger compressors, enhanced vapor injection technology, and variable-speed inverter drives to sustain performance in extreme cold.
A dual-fuel system pairs a heat pump with a gas furnace. The heat pump handles heating above a balance point, typically 25 to 35 degrees, and the furnace takes over below it. This approach captures the heat pump's efficiency advantage for the majority of the heating season while keeping the furnace as backup for the coldest nights. Dual-fuel setups make particular sense in cold climates where natural gas prices are low relative to electricity.
Mini-Split (Ductless) Heat Pumps
Mini-splits consist of an outdoor compressor unit connected to one or more indoor wall-mounted heads by refrigerant lines. Each indoor head heats and cools a single zone independently, with its own thermostat and remote control. No ductwork is needed, which makes mini-splits the go-to solution for room additions, converted garages, older homes without existing ducts, and rooms that the central system does not adequately reach.
A single outdoor unit can serve multiple indoor heads in a multi-zone configuration. A 3-zone system with one outdoor unit and three indoor heads is a common setup for a home that needs climate control in the main living area, master bedroom, and a home office. Each head operates independently, so you can heat the bedroom to 68 degrees while leaving the guest room completely off.
Installation is significantly less invasive than ducted systems. Each indoor head requires a 3-inch hole through the exterior wall for the refrigerant lines, electrical cable, and condensate drain. The outdoor unit sits on a ground-level concrete pad or a wall bracket. A skilled installer can complete a single-zone system in half a day, with multi-zone systems typically taking one to two full days.
The indoor heads are not invisible. They mount high on the wall and are approximately 32 inches wide, 12 inches tall, and 8 inches deep. Some homeowners find them aesthetically objectionable. Ceiling cassette models that mount flush in the ceiling are less visible but require ceiling cavity access for installation and future maintenance. Ducted mini-split models that hide in a closet or attic and connect to short duct runs are another option for those who want the efficiency without the wall-mounted unit.
Ground-Source (Geothermal) Heat Pumps
Ground-source heat pumps extract heat from the ground via buried loops of pipe filled with water and antifreeze solution. Below the frost line, ground temperature remains a constant 45 to 55 degrees Fahrenheit year-round regardless of surface conditions. This gives the heat pump a much more stable and warmer heat source than outdoor air during winter, resulting in the highest efficiency of any heat pump type. A COP of 4 to 5 is typical, compared to 2 to 3.5 for air-source units.
The buried loop field is the expensive part of the installation. Horizontal loops require 150 to 300 feet of trench per ton of heating capacity, dug 4 to 6 feet deep. A 3-ton system for an average home needs 450 to 900 feet of trench. Vertical loops use boreholes drilled 150 to 300 feet deep, with one or two boreholes per ton. Horizontal installations are cheaper per foot but require a large amount of open yard space. Vertical installations work on smaller lots but require a drilling rig, which increases cost.
Total installed cost for a residential ground-source system runs $20,000 to $40,000, compared to $5,000 to $15,000 for a quality ducted air-source system. The operating cost savings are real but the payback period is long, typically 10 to 15 years depending on local energy prices and climate. Ground-source makes the most financial sense for new construction where the loop installation can be completed before landscaping, and in climates with extreme temperature swings where air-source efficiency drops significantly in both summer and winter.
Efficiency Ratings Explained
SEER2 (Seasonal Energy Efficiency Ratio) measures cooling efficiency over an entire cooling season. Higher numbers are better. The minimum federal standard is 14.3 SEER2 for split systems. Good heat pumps fall in the 16 to 20 SEER2 range. Premium variable-speed models reach 22 SEER2 or higher. When comparing units, understand that the efficiency gains from 16 to 20 SEER2 cost more per point than the gains from 14 to 16, with diminishing energy savings at the top end.
HSPF2 (Heating Seasonal Performance Factor) measures heating efficiency. The minimum federal standard is 7.5 HSPF2 for split systems. Good cold-climate heat pumps achieve 10 to 12 HSPF2. If heating is your primary concern, and it usually is in northern climates, HSPF2 is the number that matters most. A unit with a slightly lower SEER2 but higher HSPF2 is often the better choice for homes that spend more months heating than cooling.
COP (Coefficient of Performance) is the simplest and most intuitive metric. It equals output BTUs divided by input BTUs. A COP of 3 means you get 3 units of heat for every 1 unit of electricity consumed. The critical detail is that COP varies with outdoor temperature. A heat pump might have a COP of 4 at 47 degrees Fahrenheit and a COP of 2 at 5 degrees. When evaluating cold-climate models, ask the installer for COP values at specific temperatures relevant to your climate, not just the rated-condition value printed on the spec sheet.
Proper Sizing
Correct sizing requires a Manual J load calculation, which accounts for your home's square footage, insulation levels (walls, attic, foundation), window area and orientation, air leakage rate, and local climate data including heating and cooling degree days. Do not let an installer size the system based on square footage alone. That shortcut routinely produces oversized systems, and oversizing is a bigger problem than undersizing.
An oversized heat pump short-cycles, turning on and off frequently rather than running in longer, steady cycles. Short-cycling reduces efficiency because the system uses the most energy during startup. It increases mechanical wear on the compressor, which shortens the equipment's lifespan. And in cooling mode, short-cycling prevents adequate dehumidification. The system cools the air temperature quickly but shuts off before it can remove enough moisture, leaving you with a cold, clammy house.
Variable-speed (inverter-driven) heat pumps are significantly more forgiving of sizing imprecision. They modulate output continuously from about 30% to 100% of rated capacity. A variable-speed system that is slightly oversized will simply run at a lower speed most of the time, maintaining comfort and efficiency. A single-speed system that is oversized has no such flexibility and will short-cycle regardless of conditions. This is one of several reasons variable-speed units are worth the price premium for most installations.
Frequently Asked Questions
Do Heat Pumps Work in Cold Climates?
Modern cold-climate heat pumps work effectively well below zero. The Mitsubishi Hyper-Heat, for example, maintains rated capacity at 5 degrees Fahrenheit and produces usable heat at minus 13 degrees. These units are less efficient at extreme cold than at moderate temperatures, but they still substantially outperform electric resistance heat at any temperature. In the coldest climates, a dual-fuel setup pairing a heat pump with a gas furnace covers all conditions efficiently, using the heat pump above 25 to 35 degrees and switching to gas below that point.
How Much Does a Heat Pump Cost to Install?
A ducted air-source heat pump replacing an existing central AC and furnace runs $5,000 to $12,000 installed, depending on the unit capacity and brand. A ductless mini-split single-zone system is $3,000 to $6,000. A multi-zone mini-split system with 3 to 4 indoor heads is $8,000 to $18,000. Ground-source geothermal systems are $20,000 to $40,000. Federal tax credits of up to $2,000 for qualifying heat pumps and state or utility rebates can significantly reduce the out-of-pocket cost. Check the DSIRE database for incentives available in your area.
Should I Replace My Furnace with a Heat Pump or Add a Mini-Split?
If your furnace and AC are both due for replacement, a ducted heat pump is the most straightforward swap. It replaces both units and uses your existing ductwork and thermostat wiring. If your furnace still has years of useful life and you want to add efficient heating and cooling to specific rooms, a mini-split is a targeted solution that does not require touching the existing system. Both approaches are valid. The right choice depends on your equipment's age, your budget, and which rooms need the most improvement.