A heat pump's rating tells you less than its capacity curve
HSPF2 is one seasonal number from a laboratory. What decides whether a ductless system heats your house on a cold night is how much heat it still makes when the outdoor air is at 5°F. ENERGY STAR publishes that figure for thousands of certified systems and almost nobody plots it. Here it is, for 92 of them.
Heating capacity of the Mitsubishi Electric MUZ-FS12NA*** at three outdoor temperatures, in BTU per hour. Paired with MSZ-FS12NA***: 14,700 at 5°F, 8,400 at 17°F, 12,300 at 47°F.
Above: the Mitsubishi Electric MUZ-FS12NA*** paired with the MSZ-FS12NA***. It holds 14,700 BTU/h at 5°F, which is 119.5% of its 47°F output. See the full spec sheet.
What is on this site
- Certified pairings101outdoor unit matched to indoor unit
- Outdoor units92one page each
- Cold-climate certified77by ENERGY STAR criteria
- Brands14as the dataset names them
- Data retrieved2026-10-16from the EPA's own API
Cold-climate certified systems with the strongest 5°F output
Ranked on the published heating capacity at 5°F as a share of the capacity at 47°F, which is arithmetic on two dataset figures and is labelled as ours wherever it appears.
| System | Brand | 5°F BTU/h | 47°F BTU/h | Share | HSPF2 |
|---|---|---|---|---|---|
| AOU9RLFF | Fujitsu | 13,400 | 9,000 | 148.9% | 11.80 |
| AOU9RLFFH | Fujitsu | 13,400 | 9,000 | 148.9% | 11.60 |
| GWH09ACD-D3DNA1A/O | GREE | 13,000 | 9,000 | 144.4% | 11.00 |
| 37MAHAQ09AA3 | Midea | 11,500 | 12,000 | 125.6% | 12.50 |
| MUZ-FS15NA*** | Mitsubishi Electric | 19,400 | 16,000 | 121.2% | 10.40 |
| MUZ-FS15NAH*** | Mitsubishi Electric | 19,400 | 16,000 | 121.2% | 9.90 |
| MUZ-FS15NA*** | Trane / Mitsubishi Electric | 19,400 | 16,000 | 121.2% | 10.40 |
| AOU15RLFF | Fujitsu | 18,100 | 15,000 | 120.7% | 10.70 |
Some of these shares are above 100%: the dataset publishes a higher capacity at 5°F than at 47°F for 27 of the units here. That is how the records read, and the dataset's own column metadata does not define which operating point each capacity represents, so the figures are printed uncorrected and explained on the methodology page.
How a page here is built
- Every figureTraceableeach spec table prints its ENERGY STAR ID and AHRI reference
- Missing dataStays visiblea blank field reads "not published", never a guess
- Model numbersExactincluding the asterisk wildcards ENERGY STAR carries
- PricesYoursno installed-cost claims; the dataset has none
Guides
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Ratings explained, October 17, 2026
SEER2 vs HSPF2: Which Rating Actually Matters?
SEER2 vs HSPF2: one rates cooling, one rates heating, and across 92 certified systems they barely track each other. What each measures and which to use.