COP to HSPF2 Conversion
Convert a heat-pump COP (a point coefficient of performance) into an approximate seasonal HSPF2 rating — a documented approximation for comparing a nameplate figure with a seasonal spec.
Calculator
COP 3.00 is roughly HSPF 10.24 — a seasonal approximation (COP is a point value; HSPF is seasonal, in BTU/Wh).
COP (Coefficient of Performance) is a unitless, single-condition efficiency: the ratio of heat delivered to electricity consumed at one operating point. HSPF2 is a seasonal rating expressed in BTU per watt-hour. Because 1 watt-hour equals 3.412 BTU, a COP can be translated into an equivalent HSPF-style figure with a simple constant — handy when a datasheet lists COP at a test temperature but you want to think in HSPF2 terms.
This converter applies that documented approximation and shows the arithmetic, so the point value and the seasonal rating can be compared on roughly the same footing.
Formula
The documented approximation used here:
HSPF2 ≈ COP × 3.412
Equivalently, COP ≈ HSPF2 ÷ 3.412. The 3.412 factor is the exact energy conversion (1 Wh = 3.412 BTU); treating the result as a seasonal HSPF2 is the approximation, since a real HSPF2 averages many operating points while a COP is measured at just one.
Approximation only. COP is a point measurement (it falls as the outdoor temperature drops); HSPF2 is the DOE 2023 seasonal test. Use the equipment’s rated HSPF2 for exact comparisons.
Worked example
Convert a COP of 3:
- HSPF2 ≈ 3 × 3.412 = 10.24
So a heat pump running at COP 3 at its test point corresponds to roughly HSPF2 10 — a strong seasonal rating, provided the unit holds that COP as the weather cools.
Why a point COP overstates seasonal HSPF2
The catch is temperature. A heat pump’s COP is highest in mild weather and falls as it gets colder; a single COP figure only describes one point on that curve. HSPF2, by contrast, is a seasonal average that already bakes in the colder hours. Converting a mild-weather COP to HSPF2 therefore overstates the seasonal number — treat the result as an optimistic ceiling unless the COP was measured at a low temperature.
To size the electricity a heat pump actually draws at a given condition, use the COP directly in a running-cost calculation rather than converting to HSPF2. And to compare a heat pump against gas heat, work in delivered cost per MMBTU on your real rates instead of comparing efficiency ratings across fuels.
Reference table
| COP | Approx. HSPF2 (COP × 3.412) |
|---|---|
| 2.0 | 6.82 |
| 2.5 | 8.53 |
| 3.0 | 10.24 |
| 3.5 | 11.94 |
| 4.0 | 13.65 |
| 4.5 | 15.35 |
| 5.0 | 17.06 |
Documented approximation (HSPF2 ≈ COP × 3.412); a point COP falls as it gets colder, so this is an optimistic seasonal figure.