Against comparable models

Each cell is the share of same-size, same-type models that the manufacturer’s typical model beats (50% is typical); the higher score is in bold. Raw medians are underneath for context: they depend on which sizes each one makes, so they are not compared.

Airdach and WILLIS on every ratingPeer scores, 0–100 · grey ticks: every ranked manufacturer · shaded: the middle half of each one’s modelsMeasured against models of the same size and duct type, WILLIS scores higher on 5 of the 6 ratings.

Airdach
WILLIS
Other ranked manufacturers

Source: AHRI Directory, NEEP · as of Oct 9, 2026

Average peer percentile, raw median and rank among ranked manufacturers
Rating	Airdach	WILLIS
Efficiency index	40%median —	63%median —
COP at 5°F	48% (higher)median 1.94	44% (higher)median 2.00
Capacity retention at 5°F	34%median 71%	71%median 90%
HSPF2	28%median 7.5	50%median 10.0
SEER2	29%median 14.3	69%median 21.0
EER2	49%median 11.4	72%median 12.5
Heating capacity at 5°F	31%median 15,700 Btu/h	65%median 19,000 Btu/h
Outdoor models	29	29
AHRI certifications	45	85

Share of models meeting each standard

Percent of each manufacturer’s models with a qualifying certification
Standard	Airdach	WILLIS
CEE 2025 Tier 1 (Split ASHP)	24.1%7 models	96.6%28 models
CEE 2026 Tier 1 (Split ASHP)	24.1%7 models	96.6%28 models
CEE Advanced Tier (Split ASHP)	0%0 models	10.3%3 models
Xcel Energy Colorado cold-climate ASHP (2025)	31%9 models	96.6%28 models
DOE Cold Climate Heat Pump Challenge	0%0 models	10.3%3 models
ENERGY STAR Cold Climate	0%0 models	86.2%25 models

Sizes and duct types offered

Models in each peer group, with the efficiency index of those models against the rest of the group.

Side by side, inside each size and duct typeShape: every model of the group · bars: each manufacturer’s middle half, median dot, 10th–90th line · 7 groups where both have models

Airdach
WILLIS
All models of the group

Raw ratings are only placed side by side within one size and duct type, where they are comparable.

Source: AHRI Directory · as of Oct 9, 2026

Models per peer group · efficiency index within the group
Size and duct type	Airdach	WILLIS
Ducted, up to 1.5 tons	2 · index —	7 · index 71%
Ducted, 2 tons	3 · index 36%	5 · index 67%
Ducted, 2.5–3 tons	7 · index 48%	3 · index 68%
Ducted, 3.5–4.5 tons	10 · index 54%	3 · index 77%
Non-ducted, up to 1.5 tons	5 · index 30%	13 · index 58%
Non-ducted, 2 tons	1 · index 25%	4 · index 63%
Non-ducted, 2.5–3 tons	1 · index 30%	6 · index 47%
Non-ducted, 3.5–4.5 tons	None	1 · index 68%

Cold-climate and all-around picks, size class by size class

Each manufacturer’s best model on each board in every size and duct type, side by side; the higher score is in bold. Both scores are 0–100 against every model of that size class (the line on each bar is 50, the typical model there), so the two compare fairly even when they make different sizes.

Cold-climate picks

Best cold-climate pick per size and duct type (keeps at least 70% of its heat at 5°F). Qualifies when its capacity retention at 5°F (capacity at 5°F as a share of capacity at 47°F) is at least 70% and Capacity retention at 5°F, COP at 5°F, HSPF2 are all rated. Score = the equal-weight mean of its peer percentiles on Capacity retention at 5°F, COP at 5°F, HSPF2 (share of the other models in its peer group it beats, 0–100), all from one certified pairing: in each duct type a model is sold in, its qualifying pairing of that type with the best score; equal scores (one decimal) go to the higher heating capacity at 5°F.
Size and duct type	AirdachCold-climate score, best model	WILLISCold-climate score, best model
Ducted, up to 1.5 tons	None on this board (0 of 2 models qualify)	69.9(50 is the typical model of its size class)PUHW09KR32-Owith ducted air handler WHEDT09K7 of 7 models qualify · AHRI 217560051
Ducted, 2 tons	None on this board (0 of 3 models qualify)	76.2(50 is the typical model of its size class)FLEX24KUHR32with ducted air handler FLEXAH24KR324 of 4 models qualify · AHRI 216720953
Ducted, 2.5–3 tons	59.2(50 is the typical model of its size class)A3TH36180OV1DGwith ducted air handler A3DH36000OE1DT1 of 7 models qualify · AHRI 218797045	87.9(50 is the typical model of its size class) (higher)HW-COND36Kwith ducted air handler HW-AHU36K4 of 4 models qualify · AHRI 216772612
Ducted, 3.5–4.5 tons	69.8(50 is the typical model of its size class)A3TH60180OV1DGwith ducted air handler A3DH60000OE1DT1 of 10 models qualify · AHRI 218797046	85.1(50 is the typical model of its size class) (higher)FLEX60KUHR32with ducted air handler FLEXAH60KR323 of 3 models qualify · AHRI 216720958
Non-ducted, up to 1.5 tons	41.6(50 is the typical model of its size class)ACSH0920VR1-D3with ductless indoor unit AIWH0900VR1-D35 of 5 models qualify · AHRI 217101992	87.2(50 is the typical model of its size class) (higher)AUHW09KR32-Owith ductless indoor unit AUHW09KR32-I13 of 13 models qualify · AHRI 217007963
Non-ducted, 2 tons	13.5(50 is the typical model of its size class)ACSH2419VR1-D3with ductless indoor unit AIWH2400VR1-D31 of 1 models qualify · AHRI 217101991	70.3(50 is the typical model of its size class) (higher)PUHW24KR32-Owith ductless indoor unit PUHW24KR32-I3 of 4 models qualify · AHRI 217007962
Non-ducted, 2.5–3 tons	22.3(50 is the typical model of its size class)ACSH3621VR1-D3with ductless indoor unit AIWH3600VR1-D31 of 1 models qualify · AHRI 217101990	77.2(50 is the typical model of its size class) (higher)MZUHW36KR32-O6 of 6 models qualify · AHRI 216772311
Non-ducted, 3.5–4.5 tons	No models in this size class	66.5(50 is the typical model of its size class)MZUHW42KR32-O1 of 1 models qualify · AHRI 216772312

All-around best

Best all-around model per size and duct type. Score = 50% heating, the mean of its peer percentiles on COP at 5°F, Capacity retention at 5°F, HSPF2, plus 50% cooling, the mean of its peer percentiles on SEER2 and EER2 (share of the other models in its peer group it beats, 0–100). All five ratings are required; there is no minimum heat kept at 5°F. In each duct type a model is sold in, it is scored on its pairing of that type with the best score; equal scores (one decimal) go to the higher cold-climate score, then the higher heating capacity at 5°F.
Size and duct type	AirdachAll-around score, best model	WILLISAll-around score, best model
Ducted, up to 1.5 tons	None on this board (0 of 2 models have all five ratings)	83.6(50 is the typical model of its size class)PUHW09KR32-Owith ducted air handler WHEDT09K7 of 7 models have all five ratings · AHRI 217560051
Ducted, 2 tons	35.7(50 is the typical model of its size class)A4TH24152MN1DLwith ducted air handler A4DH2400ME1DT1 of 3 models have all five ratings · AHRI 218331772	73.1(50 is the typical model of its size class) (higher)FLEX24KUHR32with ducted air handler FLEXAH24KR325 of 5 models have all five ratings · AHRI 216720953
Ducted, 2.5–3 tons	57.4(50 is the typical model of its size class)A3TH36180OV1DGwith ducted air handler A3DH36000OE1DT3 of 7 models have all five ratings · AHRI 218797045	82.3(50 is the typical model of its size class) (higher)HW-COND36Kwith ducted air handler HW-AHU36K3 of 3 models have all five ratings · AHRI 216772612
Ducted, 3.5–4.5 tons	59.5(50 is the typical model of its size class)A3TH60180OV1DGwith ducted air handler A3DH60000OE1DT4 of 10 models have all five ratings · AHRI 218797046	83.1(50 is the typical model of its size class) (higher)FLEX48KUHR32with ducted air handler FLEXAH48KR32Also listed as FLEX60KUHR323 of 3 models have all five ratings · AHRI 216720956
Non-ducted, up to 1.5 tons	44.9(50 is the typical model of its size class)ACSH0920VR1-D3with ductless indoor unit AIWH0900VR1-D35 of 5 models have all five ratings · AHRI 217101992	92.6(50 is the typical model of its size class) (higher)AUHW09KR32-Owith ductless indoor unit AUHW09KR32-I13 of 13 models have all five ratings · AHRI 217007963
Non-ducted, 2 tons	24.5(50 is the typical model of its size class)ACSH2419VR1-D3with ductless indoor unit AIWH2400VR1-D31 of 1 models have all five ratings · AHRI 217101991	82.1(50 is the typical model of its size class) (higher)PUHW24KR32-Owith ductless indoor unit PUHW24KR32-I4 of 4 models have all five ratings · AHRI 217007962
Non-ducted, 2.5–3 tons	30.4(50 is the typical model of its size class)ACSH3621VR1-D3with ductless indoor unit AIWH3600VR1-D31 of 1 models have all five ratings · AHRI 217101990	70.5(50 is the typical model of its size class) (higher)MZUHW30KR32-O6 of 6 models have all five ratings · AHRI 216772310
Non-ducted, 3.5–4.5 tons	No models in this size class	67.7(50 is the typical model of its size class)MZUHW42KR32-O1 of 1 models have all five ratings · AHRI 216772312

All-around board, every manufacturer

Standout model on each rating

Each manufacturer’s model that beats the largest share of comparable models on the rating; the higher share is in bold.

Top model per rating by peer percentile, with its AHRI-certified value and peer group
Rating	Airdach	WILLIS
COP at 5°F	beats 86% · 2.30A4TH42152MN1DLDucted, 3.5–4.5 tons	beats 88% · 2.10MZUHW36KR32-ONon-ducted, 2.5–3 tons
Capacity retention at 5°F	beats 55% · 73%A3TH36180OV1DGDucted, 2.5–3 tons	beats 94% · 100%AUHW24KR32-ONon-ducted, 2 tons
HSPF2	beats 64% · 8.8A3TH60180OV1DGDucted, 3.5–4.5 tons	beats 96% · 10.5HW-COND36KDucted, 2.5–3 tons
SEER2	beats 76% · 18.0A3TH60180OV1DGDucted, 3.5–4.5 tons	beats 100% · 24.5AUHW18KR32-ODucted, up to 1.5 tons
EER2	beats 83% · 12.0A4TH48152MN1DLDucted, 3.5–4.5 tons	beats 98% · 16.8AUHW09KR32-ONon-ducted, up to 1.5 tons
Heating capacity at 5°F	beats 69% · 12,100 Btu/hACSH1820VR1-D3Non-ducted, up to 1.5 tons	beats 98% · 54,000 Btu/hFLEX60KUHR32Ducted, 3.5–4.5 tons

More comparisons

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Airdach vs WILLIS heat pumps