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.

Panasonic 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, Panasonic scores higher on 4 of the 6 ratings.

Panasonic
WILLIS
Other ranked manufacturers

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

Average peer percentile, raw median and rank among ranked manufacturers
Rating	Panasonic	WILLIS
Efficiency index	68% (higher)median —	63% (higher)median —
COP at 5°F	64% (higher)median 2.00	44% (higher)median 2.00
Capacity retention at 5°F	72% (higher)median 90%	71% (higher)median 90%
HSPF2	80% (higher)median 10.3	50% (higher)median 10.0
SEER2	66%median 20.0	69%median 21.0
EER2	62%median 12.0	72%median 12.5
Heating capacity at 5°F	74% (higher)median 21,600 Btu/h	65% (higher)median 19,000 Btu/h
Outdoor models	29	29
AHRI certifications	277	85

Share of models meeting each standard

Percent of each manufacturer’s models with a qualifying certification
Standard	Panasonic	WILLIS
CEE 2025 Tier 1 (Split ASHP)	96.6%28 models	96.6%28 models
CEE 2026 Tier 1 (Split ASHP)	96.6%28 models	96.6%28 models
CEE Advanced Tier (Split ASHP)	20.7%6 models	10.3%3 models
Xcel Energy Colorado cold-climate ASHP (2025)	89.7%26 models	96.6%28 models
DOE Cold Climate Heat Pump Challenge	20.7%6 models	10.3%3 models
ENERGY STAR Cold Climate	79.3%23 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 · 8 groups where both have models

Panasonic
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	Panasonic	WILLIS
Ducted, up to 1.5 tons	6 · index 68%	7 · index 71%
Ducted, 2 tons	3 · index 64%	5 · index 67%
Ducted, 2.5–3 tons	6 · index 64%	3 · index 68%
Ducted, 3.5–4.5 tons	5 · index 52%	3 · index 77%
Non-ducted, up to 1.5 tons	9 · index 81%	13 · index 58%
Non-ducted, 2 tons	4 · index 76%	4 · index 63%
Non-ducted, 2.5–3 tons	3 · index 57%	6 · index 47%
Non-ducted, 3.5–4.5 tons	1 · index 63%	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	PanasonicCold-climate score, best model	WILLISCold-climate score, best model
Ducted, up to 1.5 tons	80.1(50 is the typical model of its size class) (higher)CU-YM9CBUCwith ducted air handler CS-YM9CD2UW5 of 6 models qualify · AHRI 218027968	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	77.1(50 is the typical model of its size class) (higher)CU-YM24CBUCwith ducted air handler CS-YM24CD1UW3 of 3 models qualify · AHRI 218027971	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	83.1(50 is the typical model of its size class)CU-5YM36CBUC5 of 6 models qualify · AHRI 218027980	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	82.7(50 is the typical model of its size class)CU-6YM48CBUC5 of 5 models qualify · AHRI 218027983	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	94.9(50 is the typical model of its size class) (higher)CU-XZ9AKUACwith ductless indoor unit CS-XZ9AKUAW9 of 9 models qualify · AHRI 214837752	87.2(50 is the typical model of its size class)AUHW09KR32-Owith ductless indoor unit AUHW09KR32-I13 of 13 models qualify · AHRI 217007963
Non-ducted, 2 tons	90.9(50 is the typical model of its size class) (higher)CU-3Z22ABUC4 of 4 models qualify · AHRI 214837935	70.3(50 is the typical model of its size class)PUHW24KR32-Owith ductless indoor unit PUHW24KR32-I3 of 4 models qualify · AHRI 217007962
Non-ducted, 2.5–3 tons	73.0(50 is the typical model of its size class)CU-5YM36CBUC3 of 3 models qualify · AHRI 218027981	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	68.7(50 is the typical model of its size class) (higher)CU-6YM48CBUC1 of 1 models qualify · AHRI 218027984	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	PanasonicAll-around score, best model	WILLISAll-around score, best model
Ducted, up to 1.5 tons	78.4(50 is the typical model of its size class)CU-YM18CBUCwith ducted air handler CS-YM18CD1UW6 of 6 models have all five ratings · AHRI 218027970	83.6(50 is the typical model of its size class) (higher)PUHW09KR32-Owith ducted air handler WHEDT09K7 of 7 models have all five ratings · AHRI 217560051
Ducted, 2 tons	78.8(50 is the typical model of its size class) (higher)CU-YM24CBUCwith ducted air handler CS-YM24CD1UW3 of 3 models have all five ratings · AHRI 218027971	73.1(50 is the typical model of its size class)FLEX24KUHR32with ducted air handler FLEXAH24KR325 of 5 models have all five ratings · AHRI 216720953
Ducted, 2.5–3 tons	84.0(50 is the typical model of its size class) (higher)CU-5YM36CBUC6 of 6 models have all five ratings · AHRI 218027980	82.3(50 is the typical model of its size class)HW-COND36Kwith ducted air handler HW-AHU36K3 of 3 models have all five ratings · AHRI 216772612
Ducted, 3.5–4.5 tons	83.9(50 is the typical model of its size class) (higher)CU-6YM48CBUC5 of 5 models have all five ratings · AHRI 218027983	83.1(50 is the typical model of its size class)FLEX48KUHR32with ducted air handler FLEXAH48KR32Also listed as FLEX60KUHR323 of 3 models have all five ratings · AHRI 216720956
Non-ducted, up to 1.5 tons	95.9(50 is the typical model of its size class) (higher)CU-XZ9AKUACwith ductless indoor unit CS-XZ9AKUAW9 of 9 models have all five ratings · AHRI 214837752	92.6(50 is the typical model of its size class)AUHW09KR32-Owith ductless indoor unit AUHW09KR32-I13 of 13 models have all five ratings · AHRI 217007963
Non-ducted, 2 tons	87.8(50 is the typical model of its size class) (higher)CU-4Z24BBUC4 of 4 models have all five ratings · AHRI 216441721	82.1(50 is the typical model of its size class)PUHW24KR32-Owith ductless indoor unit PUHW24KR32-I4 of 4 models have all five ratings · AHRI 217007962
Non-ducted, 2.5–3 tons	66.3(50 is the typical model of its size class)CU-5YM36CBUC3 of 3 models have all five ratings · AHRI 218027979	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	62.9(50 is the typical model of its size class)CU-6YM48CBUC1 of 1 models have all five ratings · AHRI 218027982	67.7(50 is the typical model of its size class) (higher)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	Panasonic	WILLIS
COP at 5°F	beats 99% · 2.51CU-YM12CBUCNon-ducted, up to 1.5 tons	beats 88% · 2.10MZUHW36KR32-ONon-ducted, 2.5–3 tons
Capacity retention at 5°F	beats 99% · 134%CU-XZ9AKUACNon-ducted, up to 1.5 tons	beats 94% · 100%AUHW24KR32-ONon-ducted, 2 tons
HSPF2	beats 99% · 11.0CU-6YM48CBUCDucted, 3.5–4.5 tons	beats 96% · 10.5HW-COND36KDucted, 2.5–3 tons
SEER2	beats 96% · 27.5CU-XZ9AKUACNon-ducted, up to 1.5 tons	beats 100% · 24.5AUHW18KR32-ODucted, up to 1.5 tons
EER2	beats 97% · 16.4CU-XZ9AKUACNon-ducted, up to 1.5 tons	beats 98% · 16.8AUHW09KR32-ONon-ducted, up to 1.5 tons
Heating capacity at 5°F	beats 99% · 22,000 Btu/hCU-2Z18ABUCNon-ducted, up to 1.5 tons	beats 98% · 54,000 Btu/hFLEX60KUHR32Ducted, 3.5–4.5 tons

More comparisons

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Panasonic vs WILLIS heat pumps