Heat Pump Efficiency Calculator

COP (coefficient of performance) is an instantaneous, lab-bench number: heat delivered divided by electricity in, both in the same units. A COP of 3.5 means you get 3.5 kWh of heat for every 1 kWh of electricity. HSPF (heating seasonal performance factor) is a seasonal average measured under the AHRI 210/240 test, expressed in BTU per watt-hour. To convert it to a seasonal COP, divide by 3.412 (the BTU-to-Wh constant): an HSPF of 9 equals a seasonal COP of about 2.64, and an HSPF of 11 (cold-climate models) equals about 3.22. HSPF is the more honest field number because it already bakes in defrost losses, part-load cycling, and the test's mix of mild and cold hours. The calculator blends both signals and then derates for your climate zone.

Air-source costs $4,000 to $10,000 installed for a typical 3-ton system, while ground-source (geothermal) runs $20,000 to $35,000 because of the buried loop field. The trade is efficiency and stability: ground-source pulls heat from soil that sits near 50 deg F all year, so it holds a real COP of 3.5 to 5.0 in any climate zone. Air-source loses efficiency below freezing because outdoor air gets harder to extract heat from. In a mild or mixed climate (DOE zones 3 to 4), air-source is the better dollar return because both systems perform well and the install cost difference takes 15 to 25 years to pay back. In very cold zones (7 to 8), ground-source or a cold-climate inverter mini-split is usually worth the premium because a standard air-source unit will lean on backup heat strips.

An air-source heat pump moves heat from outdoors to indoors, so the colder it is outside, the harder the refrigerant has to work and the lower the COP drops. A standard unit might run at COP 3.5 at 47 deg F outdoor and crash to COP 1.5 at 5 deg F, which is barely better than electric resistance. Cold-climate models (Mitsubishi Hyper-Heat, Fujitsu XLTH, Carrier Infinity Greenspeed) use variable-speed inverter compressors and enhanced vapor injection to hold COP above 2.0 down to 5 deg F and still deliver 75 to 100 percent of rated capacity. Look for an HSPF of 11 or higher and the ENERGY STAR Cold Climate label. This calculator applies a 20 percent derating to air-source in DOE zone 7-8, 10 percent in zone 5-6, and no derating to ground-source (the loop temperature does not move).

It depends on your local electricity rate, gas price, and climate zone. In mild and mixed climates with average rates (16.5 cents/kWh electricity, $1.20/therm gas), a modern air-source heat pump at seasonal COP 3.0 delivers heat for about 18.8 cents per delivered therm-equivalent, while a 95 percent AFUE gas furnace delivers heat for about 12.6 cents per therm. Gas wins on operating cost in cold zones where the heat pump derates and gas is cheap. The heat pump wins in mild zones, in areas where gas is over $2/therm (much of the Northeast and California), and against oil or propane almost everywhere because those fuels are 2 to 4 times more expensive than gas per delivered BTU. Run the comparison in this calculator with your actual utility rates.

The federal 25C Energy Efficient Home Improvement Credit covers 30 percent of the cost of a qualifying heat pump, up to $2,000 per year, through 2032. To qualify, the unit must meet the CEE highest efficiency tier (currently SEER2 16, EER2 12, HSPF2 9 or higher; ground-source has its own thresholds). On top of that, the 25D Residential Clean Energy Credit covers 30 percent of geothermal installations with no cap. Many state and utility programs stack on top: the federal HEEHRA rebate (income-qualified, up to $8,000 for a heat pump install), state programs like Mass Save and NYSERDA Clean Heat (which can add $5,000 to $10,000), and most electric utilities offer $300 to $1,500 in equipment rebates. Combined, a $12,000 cold-climate heat pump install can land at $4,000 to $6,000 out of pocket for an income-qualified household. Check DSIRE (dsireusa.org) for current programs in your ZIP code before you sign a contract.