Fujitsu AOU18RLXFWH
Matched with the ASU18RLF indoor unit, this system is certified to the ENERGY STAR cold-climate criteria and publishes 10.00 HSPF2 and 20.00 SEER2, with 19,000 BTU/h of heating at 5°F.
Heating capacity of the Fujitsu AOU18RLXFWH at three outdoor temperatures, in BTU per hour. Paired with ASU18RLF: 19,000 at 5°F, 14,600 at 17°F, 18,000 at 47°F.
- HSPF210.00Btu/Wh, seasonal heating
- SEER220.00Btu/Wh, seasonal cooling
- COP at 5°F2.18at that test point
- Capacity at 5°F19,000BTU/h
- Share of 47°F capacity105.6%ours: 5°F ÷ 47°F
What these numbers are and are not. SEER2, EER2, HSPF2 and the COP at 5°F are results from a standard rating procedure, measured at fixed temperatures and airflow in a laboratory. They are not predictions for your house, your climate or your winter. Two systems with the same HSPF2 can use different amounts of electricity in the same building, and the same system will perform differently in Boston and in Atlanta. Use the published capacity at 5°F to judge whether a system still produces heat on a cold night; use HSPF2 only to compare systems with each other.
Fujitsu AOU18RLXFWH published specifications
| Outdoor unit | AOU18RLXFWH |
|---|---|
| Indoor unit | ASU18RLF (H-Series) |
| Cold-climate certified | Yes |
| ENERGY STAR Most Efficient | Yes |
| SEER2 | 20.00 Btu/Wh |
| EER2 | 13.30 Btu/Wh |
| HSPF2 | 10.00 Btu/Wh |
| Cooling capacity | 18,000 BTU/h |
| Heating capacity at 47°F | 18,000 BTU/h |
| Heating capacity at 17°F | 14,600 BTU/h |
| Heating capacity at 5°F | 19,000 BTU/h |
| COP at 5°F | 2.18 |
| Compressor staging | Continuously variable |
| Refrigerant | R-410A |
| Date certified | 2026-06-05 |
| ENERGY STAR ID / AHRI reference | 2417184 / 8779045 |
| 5°F capacity as a share of 47°F (ours) | 105.6% |
| Capacity class (ours) | 18,000 BTU/h nominal |
Source. ENERGY STAR Certified Heat Pumps, U.S. EPA, retrieved 2026-10-16 from the dataset's Socrata API. Record identified by ENERGY STAR ID 2417184, AHRI reference 8779045. Certification partner: Fujitsu General America, Inc.. Model numbers are reproduced exactly as published, including the asterisks ENERGY STAR carries as the manufacturer's wildcard for trim variants.
What the published capacities say about cold weather
A heat pump moves heat from outdoor air, so the colder that air gets, the less heat there is to move. The dataset publishes capacity at three outdoor temperatures, and the shape between them is the single most useful thing on this page. For the AOU18RLXFWH paired with the ASU18RLF:
- At 47°F it delivers 18,000 BTU/h.
- At 17°F it delivers 14,600 BTU/h.
- At 5°F it delivers 19,000 BTU/h, which is 105.6% of the 47°F figure.
That 5°F figure is higher than the 47°F figure. This is common in the dataset and is not an error in it: variable-speed systems are often rated at a maximum output at low temperature while the 47°F row reports a different operating point, and the dataset's own column metadata does not define which point each capacity represents. The figures are printed here as published, without correction, and the methodology page explains the gap.
ENERGY STAR lists this system as meeting its cold-climate criteria, which the program describes as better low-temperature heating performance, suitable for use as a home's sole heating source. That is the program's judgement on the published test data, not a promise about any particular winter or any particular house.
Running cost for a 18,000 BTU/h system like this one
Worked as an illustration, not a quote: a house that burned 600 therms of gas in a year through an 80% AFUE furnace needed about 48.0 million BTU of delivered heat. At $1.50 a therm that gas cost $900. Delivering the same heat with a heat pump rated at 10.00 HSPF2 takes 4,800 kWh, which at $0.18 a kWh costs $864. The two costs are equal at $0.188 a kWh.
Those four prices are not your prices, and HSPF2 is a rating-condition figure rather than a seasonal measurement for your climate. Change every input in the running-cost calculator, which shows each formula as it works.
Comparable systems
Same nominal capacity class (18,000 BTU/h), closest published HSPF2 to this one. Colour marks cold-climate certification.
-
DELLA 048-C-TP-18K2V-23S-OUT
Cold-climate
HSPF2 10.00 · SEER2 23.00 · 13,600 BTU/h at 5°F
-
DELLA 048-C-TPH-18K2V-23S-OUT
Cold-climate
HSPF2 10.00 · SEER2 23.50 · 17,800 BTU/h at 5°F
-
Mitsubishi Electric MUZ-FS18NAH***
Cold-climate
HSPF2 10.30 · SEER2 21.00 · 22,400 BTU/h at 5°F
-
Daikin RXF18AXVJU
Standard
HSPF2 9.60 · SEER2 21.00 · 10,700 BTU/h at 5°F
-
Daikin RXF18BVJU*
Cold-climate
HSPF2 9.60 · SEER2 21.00 · 15,200 BTU/h at 5°F
More: all 92 certified systems, or the explainer on SEER2 vs HSPF2.