What a Heat Pump Is and Why It Beats Resistance Heat
A heat pump is a refrigerant-cycle machine that moves thermal energy from one reservoir to another. The same hardware that cools your house in summer reverses in winter, pulling heat from outdoor air, ground, or water and delivering it indoors.[6] The compressor, condenser, expansion valve, and evaporator are identical to an air conditioner; a four-way reversing valve flips the refrigerant flow direction on demand.
The efficiency advantage shows up directly in the seasonal metric. A heat pump rated at HSPF2 8.5 delivers 8.5 BTU of heating per Wh of electricity averaged across a standard heating season, equivalent to a seasonal COP of about 2.49 since 3.41 BTU/Wh corresponds to COP 1.0.[1] Electric baseboard, by contrast, is fixed at exactly 3.41 BTU/Wh (COP 1.0) no matter the outdoor temperature.
| System | Rating metric | Typical 2026 value | BTU per kWh delivered |
|---|---|---|---|
| Electric resistance baseboard | COP | 1.00 | 3,412 |
| Federal-minimum split-system heat pump (north) | HSPF2 | 7.5 | 7,500 |
| ENERGY STAR Version 6.1 heat pump | HSPF2 | ≥ 8.1 | ≥ 8,100 |
| CCASHP-listed cold-climate heat pump (typical) | HSPF2 | 9.0–11.0 | 9,000–11,000 |
| Ground-source heat pump (residential) | COP @ 32°F EWT | 3.5–4.5 | 11,940–15,354 |
The practical implication is concrete. A house that needs 30,000 BTU/hr at design temperature consumes about 8.8 kW continuous from electric baseboard, roughly 3.6 kW from a federal-minimum heat pump, and roughly 2.5 kW from an ENERGY STAR unit running at its seasonal average.[3]
Over a 1,500-hour heating season, the 1.1 kW gap between federal-minimum and ENERGY STAR equates to roughly 1,650 kWh saved per year, or about $269 at the US 2024 average residential electricity price.[9]
How Heat Pumps Are Rated (and What Those Numbers Actually Mean)
AHRI Standard 210/240-2023 defines the test conditions under which manufacturers measure capacity and efficiency.[1] Cooling capacity is rated at 95°F outdoor dry bulb and 80°F indoor dry bulb (with 67°F indoor wet bulb to fix latent conditions). Heating "high-temperature" capacity is rated at 47°F outdoor and 70°F indoor. A "low-temperature" heating rating at 17°F is also required, and cold-climate certified units publish an additional point at 5°F.
| Test | Outdoor | Indoor | Metric produced |
|---|---|---|---|
| Cooling A2 | 95°F DB | 80°F DB / 67°F WB | Nominal cooling capacity, SEER2 |
| Cooling B2 | 82°F DB | 80°F DB / 67°F WB | Part-load cooling, contributes to SEER2 |
| Heating H1 | 47°F DB | 70°F DB | Nominal heating capacity, contributes to HSPF2 |
| Heating H2 | 35°F DB | 70°F DB | Frost-defrost cycle data |
| Heating H3 | 17°F DB | 70°F DB | Low-temperature heating capacity |
| Heating H4 (CCASHP) | 5°F DB | 70°F DB | Cold-climate heating capacity |
These rating points matter because heat pump capacity is not constant across outdoor temperature. The label says "3 tons" (36,000 BTU/hr) and that figure refers strictly to the 47°F heating point or the 95°F cooling point. At any other temperature, you read the manufacturer's published expanded performance data, not the nameplate.
The seasonal metrics (SEER2 for cooling, HSPF2 for heating) are weighted averages across many bin temperatures, accounting for capacity drop, defrost penalty, and part-load behavior.[1] SEER2 replaced SEER under AHRI 210/240-2023, and the change was not cosmetic: the test now uses higher external static pressure to better reflect installed ductwork, which lowered reported efficiency numbers across the board by roughly 4-5% even though equipment performance was unchanged.
| Tier | Region | SEER2 min | HSPF2 min | Source |
|---|---|---|---|---|
| Federal minimum | North | 14.3 | 7.5 | DOE 10 CFR 430 |
| Federal minimum | South / Southwest | 15.2 | 7.5 | DOE 10 CFR 430 |
| ENERGY STAR v6.1 | All US | 15.2 | 8.1 | ENERGY STAR program |
| ENERGY STAR v6.1 Cold Climate | Northern climate option | 15.2 | 9.0 | ENERGY STAR program |
| IRA 25C qualifying | All US | ≥ 15.2 (CEE Tier) | ≥ 8.1 (CEE Tier) | IRS Fact Sheet 25C |
Reading manufacturer spec sheets: the AHRI Certified Reference Number (ARN) on the equipment label maps to a row in the public AHRI directory at ahridirectory.org. That row lists SEER2, HSPF2, EER2, and the H1 / H3 capacity points, all independently verified figures, not marketing claims.[1] If a contractor quotes capacity numbers that conflict with the AHRI directory, the directory wins.
Capacity Drops as Outdoor Temperature Drops
Every air-source heat pump loses heating capacity as it gets colder outside, because there is less heat available in the outdoor air to extract. How fast capacity drops separates a standard heat pump from a cold-climate heat pump.
A standard residential split-system heat pump nominally rated at 36,000 BTU/hr (3 tons) at 47°F typically delivers about 19,000-22,000 BTU/hr at 17°F (53-61% of rated) and 12,000-14,000 BTU/hr at 5°F (33-39% of rated).[5]
A NEEP-listed cold-climate unit of the same nominal size must deliver at least 25,200 BTU/hr at 17°F (70% of 47°F capacity) and at least 20,880 BTU/hr at 5°F (58%) to qualify for the Version 4.0 specification.[4]
The implication for sizing is direct. In a Minneapolis design temperature of −11°F, a standard heat pump rated 36,000 BTU/hr at 47°F provides only about 8,000-10,000 BTU/hr at design. A 36,000 BTU/hr CCASHP unit holds roughly 18,000-22,000 BTU/hr at the same temperature, more than double the standard equipment's output drawn from the same nameplate tonnage.[4]
The seasonal efficiency hit at low temperature is also meaningful. A standard heat pump's COP drops from roughly 3.5 at 47°F to about 1.8-2.0 at 17°F and 1.2-1.5 at 5°F. A cold-climate unit holds COP closer to 2.5 at 17°F and 2.0 at 5°F.[5]
A COP of 2.0 still beats electric resistance (COP 1.0) by a factor of two, which is why CCASHP equipment can carry the heating load all the way down to single-digit temperatures without aux heat in most US locations.
The Four System Types and How to Pick Between Them
US residential heat pumps come in four configurations, distinguished by heat source (air, ground, water) and distribution method (ducted, ductless).
| System type | Heat source | Distribution | Installed cost (typical) | Seasonal efficiency | Best fit |
|---|---|---|---|---|---|
| Air-source ducted (split system) | Outdoor air | Existing ductwork | $5,000–$10,000 | HSPF2 7.5–10.5 | Homes with existing AC ductwork |
| Air-source ductless (mini-split) | Outdoor air | Per-zone wall/ceiling head | $3,000–$8,000 per zone | HSPF2 8.5–12.0 | Homes without ducts, additions, retrofits |
| Ground-source (closed loop) | Below-frost-line earth | Existing ductwork or hydronic | $20,000–$30,000 | COP 3.5–4.5 (steady) | New construction, high heating demand, owner-occupied long term |
| Water-source / open loop | Well, pond, aquifer | Ductwork or hydronic | $15,000–$25,000 | COP 4.0–5.0 | Properties with abundant clean water |
Air-source ducted units dominate US installations because most existing houses already have ductwork from a prior furnace or AC. The retrofit is straightforward: swap the outdoor condenser and the indoor coil, keep the duct system in place, and the new equipment runs.[6] Where ducts leak heavily (more than ~15% loss to unconditioned space), duct sealing is the prerequisite, since a leaky duct system wastes 20-30% of any heat pump's output regardless of efficiency tier.
Air-source ductless mini-splits skip ductwork entirely. A single-zone unit puts one indoor head on one wall; a multi-zone unit links several heads to one outdoor compressor via refrigerant lineset. They make sense for houses without ducts (most pre-1960 homes in the Northeast, for example), for additions, and for converting electric-baseboard houses to heat pumps.[6] Per-zone control is the major comfort advantage; the visible indoor head is the major aesthetic disadvantage.
Ground-source (geothermal) systems exchange heat with the earth at a stable 45-55°F year-round, instead of with outdoor air that swings from −20°F to 95°F.
Because the source temperature is steady, the COP is steady, typically 3.5-4.5 in heating and 4.0-5.0 in cooling, with no winter capacity loss.[14] The installation cost is dominated by the buried ground loop, which is why new construction (where excavation is happening anyway) is the natural fit.
Water-source heat pumps exchange heat with a well, pond, or aquifer. They are uncommon in retrofits because they require a suitable water resource and local permitting, but where the resource exists they outperform ground-source systems on both cost and efficiency.[14] Open-loop systems pull water continuously from a source and return it downstream; closed-loop submerged-pond systems are essentially ground-source with the pipe in water instead of earth.
Federal and State Incentives in 2026
Two distinct federal programs apply to heat pump installations in 2026, and they stack with each other and with state and utility rebates.
| Program | Maximum amount | How it works | Eligibility / requirements |
|---|---|---|---|
| IRA Section 25C (Energy Efficient Home Improvement Credit) | $2,000 per year | Non-refundable tax credit, 30% of installed cost up to cap | Equipment must meet CEE highest tier (typically ENERGY STAR Cold Climate or HSPF2 ≥ 8.1) |
| IRA Section 50122 (HEEHRA point-of-sale rebate) | $8,000 | Reduced sticker price at install, administered by state energy office | Household income ≤ 80% Area Median Income for full rebate; 80-150% AMI for 50% rebate |
| IRA Section 50121 (HOMES rebate) | Up to $8,000 (modeled) / $4,000 (measured) | Whole-home performance rebate based on energy savings | Project must achieve modeled or measured energy reduction ≥ 20-35% |
The 25C tax credit is the simplest path and is available to any taxpayer regardless of income, but it requires the equipment to meet the Consortium for Energy Efficiency's highest performance tier — in practice ENERGY STAR Version 6.1 Cold Climate or equivalent (HSPF2 ≥ 8.1, SEER2 ≥ 15.2) for split-systems.[7]
The credit is non-refundable, meaning it can zero out federal tax liability but cannot produce a refund larger than tax owed; unused credit does not roll forward to future years for Section 25C as of 2026.
HEEHRA is administered at the state level and rolled out unevenly through 2024 and 2025; most states began accepting applications in 2025-2026.[8] The income test uses Area Median Income (AMI) by household size for the applicant's county, which means the same income qualifies in different ways depending on where the household lives. Check your state energy office's program page for current intake status.
State and utility rebates layer on top. Mass Save offers up to $10,000 per home for whole-house heat pump conversions in Massachusetts. NYSERDA's Comfort Home program offers structured rebates for heat pump installations in New York. Most western utilities (PG&E, SoCal Edison, NV Energy) offer $500-$1,500 per ton for ENERGY STAR heat pumps. The stack (25C + HEEHRA + state + utility) can reduce out-of-pocket cost by $5,000-$15,000 for a qualifying household.
Operating Cost Versus Furnaces and Resistance Heat
The headline cost-per-BTU comparison depends entirely on local utility prices, but the math is portable to any zip code.
Calculating it for the US average: a federal-minimum heat pump (HSPF2 7.5) delivers 7,500 BTU per kWh of electricity consumed seasonally. At the 2024-2025 US residential average of $0.163/kWh, that comes to about $21.73 per million BTU delivered.[9]
A 95% AFUE natural gas furnace delivers 0.95 × 100,000 = 95,000 BTU per therm of gas consumed; at the US average residential gas price of about $1.30 per therm, that comes to about $13.68 per million BTU delivered.[10]
| System | Seasonal efficiency | Fuel price (US avg) | Cost per MMBTU delivered |
|---|---|---|---|
| Electric resistance baseboard | COP 1.00 | $0.163/kWh | $47.77 |
| Federal-minimum heat pump | HSPF2 7.5 | $0.163/kWh | $21.73 |
| ENERGY STAR v6.1 heat pump | HSPF2 8.1 | $0.163/kWh | $20.12 |
| CCASHP heat pump (typical) | HSPF2 9.5 | $0.163/kWh | $17.16 |
| 80% AFUE natural gas furnace | 80% | $1.30/therm | $16.25 |
| 95% AFUE natural gas furnace | 95% | $1.30/therm | $13.68 |
| Oil furnace (138,500 BTU/gal) | 85% | $3.85/gal | $32.69 |
| Propane furnace (91,500 BTU/gal) | 95% | $2.85/gal | $32.79 |
At national average prices, natural gas at 95% AFUE still beats heat pumps slightly on raw operating cost. But that ranking flips quickly with local conditions. In states with electricity below $0.12/kWh (most Pacific Northwest, Tennessee, Kentucky) a federal-minimum heat pump beats gas. In states with electricity above $0.25/kWh (California, Massachusetts, Hawaii) gas wins comfortably unless the heat pump is high-HSPF2.
The other reason heat pumps win in many cases is that they deliver cooling as well as heating from the same equipment. A house with both AC and gas furnace is paying for two systems; a heat pump replaces both. When the heat pump install cost is compared against the combined replacement cost of AC plus furnace (rather than furnace alone), the breakeven on operating cost moves substantially in the heat pump's favor.
Electric prices are also decoupling from heating prices via solar PV. A household with rooftop solar that exports excess summer generation effectively buys winter heating electricity at the avoided-cost rate, often below the residential retail rate.[9] Where net metering is favorable, heat pump operating cost can fall by 30-50% relative to grid-only rates.
When a Heat Pump Makes Economic Sense
The heat pump versus fossil furnace decision is rarely about climate alone in 2026. The decision turns on five variables: existing equipment age, fuel prices, electricity prices, incentive eligibility, and whether the home already has central AC.
Households replacing a 15-year-old AC and a 20-year-old gas furnace in a climate with both heating and cooling demand typically come out ahead with a heat pump on lifecycle cost, because one piece of equipment replaces two.[6] Households with a brand-new gas furnace and no AC face a harder math problem; the heat pump install displaces equipment that has 15 years of useful life remaining.
The climate test is more nuanced than the conventional wisdom suggests. Air-source heat pumps work effectively in every US climate zone provided the equipment is appropriately specified. Northern installations need CCASHP-rated equipment sized to a low balance point, plus electric or fossil aux for the coldest hours. Southern installations don't need CCASHP-rated equipment and can use standard heat pumps with very low aux runtime.[4]
The eligibility test changes the calculation substantially. A household qualifying for full HEEHRA at 80% AMI receives up to $8,000 off the install at the point of sale, plus the $2,000 25C tax credit, plus typically $1,000-$3,000 in state or utility rebates, bringing a $10,000 standard heat pump install to roughly net $0 to $3,000 out of pocket.[8] At those prices, the operating cost question becomes secondary.
Sizing and Aux Heat: The Two Decisions That Dominate Outcomes
Two decisions made before any equipment ships determine whether a heat pump installation succeeds or fails: the size of the equipment, and how much aux heat it relies on. Both decisions are downstream of a single document, the Manual J load calculation.[13]
Sizing decision. Heat pumps must handle two loads (heating and cooling) that are rarely equal at the same house. In Miami the cooling load is typically 3-4× the heating load; in Minneapolis it is the reverse. The size that perfectly matches one load almost certainly mismatches the other, which is why every honest heat pump quote starts from a Manual J that reports both numbers.
Aux heat decision. Aux heat is electric resistance backup (typically 5, 10, 15, or 20 kW strip kits, occasionally a gas furnace in "dual fuel" installations) that supplements the heat pump when outdoor temperature drops below the balance point. The balance point is the temperature at which the heat pump's available capacity equals the home's heating load; above it the heat pump alone keeps up, below it aux fills the gap.[4] Picking a higher balance point means smaller, cheaper equipment but more aux runtime; picking a lower balance point means larger equipment or CCASHP equipment with less aux.
Cost implication. At the US average electricity price, electric aux heat runs at roughly $47.77 per million BTU delivered, more than three times the cost per BTU of the heat pump itself running at HSPF2 8. A heat pump that runs aux 200 hours per winter at 10 kW delivers 2,000 kWh × $0.163 = $326 of aux electricity per year; the same heating delivered by the heat pump alone would cost roughly $115. Over a 15-year equipment life, that aux-heavy install pays an extra $3,000 in electricity that a CCASHP unit at the same install location would have avoided.
For the detailed methodology, the heat pump sizing article walks through balance-point design with worked examples. For aux-heat behavior in detail, auxiliary heat covers the four scenarios when aux is normal and the four scenarios when it signals a problem.
The 2025 Refrigerant Transition and What It Means for Buyers
The EPA's AIM Act final rule banned the manufacture of new residential AC and heat pump equipment using R-410A refrigerant after January 1, 2025.[12] The transition is the largest refrigerant change in two decades and affects every heat pump quote in 2026.
Two refrigerants dominate the replacement landscape. R-454B (sold as Opteon XL41) has a global warming potential of 466, compared to R-410A's GWP of 2,088. R-32 (used widely in Asia for a decade and now in US Daikin, Mitsubishi, Carrier and others) has a GWP of 675.[12] Both are classified A2L, meaning mildly flammable but lower-toxicity, with stricter installation requirements than the A1-classified R-410A they replace.
Technician implications matter for buyers because the A2L classification adds installation requirements that R-410A did not have. Outdoor unit setbacks from windows and openings are larger, indoor unit line-set length limits are different, and brazing requires a nitrogen purge to prevent ignition of residual refrigerant.
None of this changes the equipment's operating characteristics for the homeowner, but it changes the install cost slightly, typically $200-$500 per system above the 2024 baseline for the additional materials and labor.
Efficiency implications are positive. R-32 in particular allows higher-pressure operation and tighter heat exchangers, which is why several manufacturers' R-32 models report HSPF2 numbers 0.5-1.0 higher than equivalent R-410A predecessors at the same nominal tonnage.[3] The seasonal efficiency improvement partially offsets the slightly higher install cost and entirely offsets it over the equipment's life via reduced electricity consumption.
What This Cluster Covers
The cluster organizes heat pump content into four functional areas, each with its own depth.
Sizing and selection
- Heat pump sizing — balance-point methodology, dual-load problem, when CCASHP equipment changes the math
- Heat pump aux heat — when resistance strips engage, what they cost, when frequent aux signals an undersized unit
- Aux heat vs emergency heat — automatic vs manual operation, thermostat configuration
Performance metrics
- Seasonal performance factor — the whole-system seasonal-COP metric that captures real-world performance including aux runtime
Cold-climate operation
- Heat pump defrost cycle — why coils ice over, what defrost does, how CCASHP units manage it
Related load and equipment topics
- Manual J load calculation — the ACCA methodology that produces the loads any heat pump quote should reference
- Manual S equipment selection — the rules for matching nameplate capacity to Manual J load
- Building science fundamentals — envelope drivers (R-value, U-factor, infiltration) that shift the loads
Calculators
- Heat pump size calculator — dual-load math with balance-point estimate, CCASHP toggle, and 6 worked examples by home size
- BTU calculator — coarser whole-house or single-room sizing
- Manual J load calculator — full envelope load math approximating Manual J for planning purposes