Why 5°F and −13°F matter more than SEER2
NEEP created its Cold Climate Air Source Heat Pump (ccASHP) specification because the standard seasonal metric, HSPF, "does not include low temperature testing points below 17°F" — so a unit can post an excellent seasonal rating while losing most of its output on the coldest nights of the year (NEEP ccASHP Specification and Product List). The spec is meant "to identify air source heat pumps that are best suited to heat efficiently in cold climates (IECC climate zone 4 and higher)" and its accompanying product list is described as "a one-stop-shop for cold-climate qualified air source heat pumps" (NEEP). Version 4.0 of the specification took effect January 1, 2023, and qualification requires a COP above 1.75 at 5°F, HSPF2 ≥ 8.5 / SEER2 ≥ 15 for non-ducted systems, and HSPF2 ≥ 7.7 / SEER2 ≥ 14.3 for ducted systems (NEEP/NEEA product list refresher). That's why capacity retention at 5°F, and output at a unit's lowest cataloged temperature (commonly −13°F or −15°F), tell you more about whether a heat pump will actually carry your home's heating load on a design day than a headline SEER2 or HSPF2 number ever will.
ENERGY STAR's Cold Climate bar
Under ENERGY STAR's key product criteria, a certified Cold Climate split heat pump must meet at least 8.5 HSPF2 (non-ducted) or 8.1 HSPF2 (ducted), with 15.2 SEER2 in both cases, plus two low-ambient requirements: a coefficient of performance (COP) at 5°F of at least 1.75, and heating capacity at 5°F equal to at least 70% of capacity at 47°F (ENERGY STAR Air-Source Heat Pumps key product criteria; ENERGY STAR Heat Pump Version 6.2 Specification, revised February 2026). For comparison, the baseline (non-cold-climate) ENERGY STAR split heat pump only needs 7.8 HSPF2. A separate, stricter federal target — the DOE Residential Cold Climate Heat Pump Challenge — asks for 100% capacity retention at 5°F with a COP of 2.1, a bar only a handful of the models below actually clear (Carrier cold-climate heat pump brochure).
The comparison
All 10 models below are marketed as cold-climate or extended-low-temperature products. Capacities marked (max) are the compressor's highest output at that temperature rather than the AHRI-rated full-load point — NEEP publishes both, and for cold-climate sizing, maximum output at low temperature is what actually determines whether a unit can carry the load unassisted.
Three familiar names that aren't on NEEP's cold-climate list
Carrier's Infinity 24 Greenspeed (25VNA4), Trane's XV20i (4TWV0), and York's Affinity YZV are all marketed with strong efficiency claims, but none of the three appears anywhere in NEEP's 154,637-row ccASHP export, and none publishes a rated heating capacity or COP at 5°F. Their stated minimum operating temperatures — −15°F for the 25VNA4, −10°F for the XV20i — describe whether the compressor turns on, not how much heat it can deliver once it does. If you're comparing on cold-climate performance specifically, here's what each manufacturer's actual NEEP-listed cold-climate product looks like instead:
Carrier — Infinity 21 VS Cold Climate (27VNA1)
- Cap. @ 47°F
- 52,500 Btu/h
- Cap. @ 5°F
- 52,000 Btu/h
- Retention @ 5°F
- 99%
- HSPF2 / SEER2
- 12.0 / 18.5
- COP @ 5°F
- 2.02
- NEEP listed
- Yes
R-454B refrigerant. Source: NEEP · Carrier
Trane — 20 TruComfort Variable Speed (5TWV0)
- Cap. @ 47°F
- 33,900 Btu/h (max)
- Cap. @ 5°F
- 23,800 Btu/h
- Retention @ 5°F
- 73%
- HSPF2 / SEER2
- 9.4 / 20.0
- COP @ 5°F
- 2.10
- NEEP listed
- Yes
R-454B refrigerant, Trane's current XV20i successor line. Source: NEEP
York (Johnson Controls)
- NEEP-listed successor
- None found
A full scan of every row in NEEP's export found no York cold-climate ducted product under any current series name (LX, MH/MJ, Y400/Y600/Y800, YD5/YDC/YDV, PH9). Source: NEEP
What the numbers show
A few patterns hold across all 10 models researched for this page:
- The three lines missing from NEEP's list publish the least low-temperature data. Carrier's 25VNA4, Trane's XV20i, and York's Affinity YZV all lack a published 5°F rating, and their minimum-temperature claims describe operability, not capacity.
- Refrigerant is shifting. The newest listings here use R-32 (Daikin AURORA, Fujitsu XLTH, Gree Sapphire R-32) or R-454B (Bosch IDS Ultra, Carrier 27VNA1, Trane 5TWV0), while the legacy Mitsubishi Hyper-Heat and LG LGRED° lines shown remain R-410A.
- Retention above 100% is normal for ductless mini-splits — the AHRI-rated 47°F point sits well below what an inverter compressor can actually put out, so Mitsubishi's FS line reaches 117% and Gree's Sapphire lines land at 100–111%. Ducted variable-speed systems cluster lower — Trane's 5TWV0 at 73%, Bosch's IDS Ultra at 100%.
- COP at 5°F clusters tightly between 1.80 and 2.14 across nearly every listed model, which means low-temperature capacity — not efficiency — is usually the real differentiator when sizing for a cold-climate design day.
How to use this if you're shopping
Two things matter more than any spec sheet headline. First, verify the exact outdoor-and-indoor unit combination your installer is quoting on NEEP's ccASHP list or the AHRI certified directory — SEER2, HSPF2, and cold-weather capacity all shift with the paired indoor unit, sometimes significantly. Second, ask what the unit's rated (not "up to") heating capacity is at your region's 99% design temperature, not just at 47°F — a system that's undersized at 5°F will lean harder on backup resistance heat exactly when electricity demand (and your bill) is highest. Run those numbers through the Heat Pump vs. Traditional HVAC calculator once you have a specific model in mind.