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, WILLIS scores higher on 4 of the 6 ratings.

Panasonic
WILLIS
Other ranked manufacturers

Source: AHRI Directory, NEEP · as of Oct 11, 2026

Average peer percentile, raw median and rank among ranked manufacturers
Rating	Panasonic	WILLIS
Efficiency index	47%median —	51%median —
COP at 5°F	40% (higher)median 1.90	39% (higher)median 1.84
Capacity retention at 5°F	50%median 68%	64%median 76%
HSPF2	57% (higher)median 9.2	52% (higher)median 9.0
SEER2	48%median 17.8	55%median 21.0
EER2	39%median 10.7	46%median 12.0
Heating capacity at 5°F	53%median 15,150 Btu/h	68%median 13,600 Btu/h
Outdoor models	36	15
AHRI certifications	56	29

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)	52.8%19 models	86.7%13 models
CEE 2026 Tier 1 (Split ASHP)	47.2%17 models	80%12 models
CEE Advanced Tier (Split ASHP)	0%0 models	0%0 models
Xcel Energy Colorado cold-climate ASHP (2025)	36.1%13 models	86.7%13 models
DOE Cold Climate Heat Pump Challenge	0%0 models	0%0 models
ENERGY STAR Cold Climate	36.1%13 models	73.3%11 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

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 11, 2026

Models per peer group · efficiency index within the group
Size and duct type	Panasonic	WILLIS
Ducted, up to 1.5 tons	7 · index 51%	1 · index 32%
Ducted, 2 tons	3 · index 53%	1 · index 46%
Ducted, 2.5–3 tons	5 · index 46%	4 · index 51%
Ducted, 3.5–4.5 tons	3 · index 53%	2 · index 55%
Ducted, 5 tons and up	1 · index 42%	None
Non-ducted, up to 1.5 tons	16 · index 47%	8 · index 44%
Non-ducted, 2 tons	4 · index 40%	1 · index 72%
Non-ducted, 2.5–3 tons	1 · index 37%	3 · 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	64.3(50 is the typical model of its size class) (higher)CU-HE18YAHK6with ducted air handler CS-HE18YAC64 of 7 models qualify · AHRI 212396504	36.0(50 is the typical model of its size class)MZUHW18KCH21S2-O1 of 1 models qualify · AHRI 214810334
Ducted, 2 tons	67.3(50 is the typical model of its size class) (higher)CU-E24YAHK6with ducted air handler CS-HE24YAC63 of 3 models qualify · AHRI 212396499	50.1(50 is the typical model of its size class)MZUHW24KCH21S2-O1 of 1 models qualify · AHRI 214810335
Ducted, 2.5–3 tons	78.6(50 is the typical model of its size class) (higher)CU-HE36YAHK6with ducted air handler CS-HE36YAC62 of 5 models qualify · AHRI 212396507	55.3(50 is the typical model of its size class)FLEX24/36KUHwith ducted air handler FLEXAH24/36K4 of 4 models qualify · AHRI 214137765
Ducted, 3.5–4.5 tons	73.8(50 is the typical model of its size class) (higher)CU-HE48YAHK6with ducted air handler CS-HE48YAHK62 of 3 models qualify · AHRI 212396496	56.7(50 is the typical model of its size class)FLEX48/60KUHwith ducted air handler FLEXAH48/60K2 of 2 models qualify · AHRI 214797686
Ducted, 5 tons and up	None on this board (0 of 1 models qualify)	No models in this size class
Non-ducted, up to 1.5 tons	87.4(50 is the typical model of its size class) (higher)CU-XE9WKUAwith ductless indoor unit CS-XE9WKUAW6 of 16 models qualify · AHRI 205047851	73.5(50 is the typical model of its size class)MZUHW18KCH21S2-O7 of 8 models qualify · AHRI 214810331
Non-ducted, 2 tons	64.2(50 is the typical model of its size class)CU-XE24WKUAwith ductless indoor unit CS-XE24WKUAW2 of 4 models qualify · AHRI 205047855	76.1(50 is the typical model of its size class) (higher)MZUHW24KCH21S2-O1 of 1 models qualify · AHRI 214810332
Non-ducted, 2.5–3 tons	None on this board (0 of 1 models qualify)	73.7(50 is the typical model of its size class)MZUHW42KCH21S2-O3 of 3 models qualify · AHRI 214810330

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	75.4(50 is the typical model of its size class) (higher)CU-E9SD3UAwith ducted air handler CS-E9SD3UAW7 of 7 models have all five ratings · AHRI 9125308	31.5(50 is the typical model of its size class)MZUHW18KCH21S2-O1 of 1 models have all five ratings · AHRI 214810334
Ducted, 2 tons	65.8(50 is the typical model of its size class) (higher)CU-HE24YAHK6with ducted air handler CS-HE24YAHK63 of 3 models have all five ratings · AHRI 212396493	45.9(50 is the typical model of its size class)MZUHW24KCH21S2-O1 of 1 models have all five ratings · AHRI 214810335
Ducted, 2.5–3 tons	56.1(50 is the typical model of its size class) (higher)CU-HE36YAHK6with ducted air handler CS-HE36YAHK65 of 5 models have all five ratings · AHRI 212396495	53.1(50 is the typical model of its size class)MZUHW30KCH21S2-O4 of 4 models have all five ratings · AHRI 214810336
Ducted, 3.5–4.5 tons	53.3(50 is the typical model of its size class)CU-HE55YAHK6with ducted air handler CS-HE60YAHK63 of 3 models have all five ratings · AHRI 212396497	57.4(50 is the typical model of its size class) (higher)PRT60KUH2 of 2 models have all five ratings · AHRI 214137764
Ducted, 5 tons and up	41.7(50 is the typical model of its size class)CU-E60YAHK6with ducted air handler CS-HE60YAHK61 of 1 models have all five ratings · AHRI 212396491	No models in this size class
Non-ducted, up to 1.5 tons	92.0(50 is the typical model of its size class) (higher)CU-XE9WKUAwith ductless indoor unit CS-XE9WKUAW14 of 16 models have all five ratings · AHRI 205047851	63.8(50 is the typical model of its size class)HW12KUHR410A-Owith ductless indoor unit HW12KUHR410A-I8 of 8 models have all five ratings · AHRI 216772615
Non-ducted, 2 tons	73.7(50 is the typical model of its size class) (higher)CU-4E24RBU-54 of 4 models have all five ratings · AHRI 10221204	71.5(50 is the typical model of its size class)MZUHW24KCH21S2-O1 of 1 models have all five ratings · AHRI 214810332
Non-ducted, 2.5–3 tons	36.8(50 is the typical model of its size class)CU-5E36QBU-51 of 1 models have all five ratings · AHRI 10221207	70.2(50 is the typical model of its size class) (higher)MZUHW42KCH21S2-O3 of 3 models have all five ratings · AHRI 214810330

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 90% · 2.24CU-E18RKUANon-ducted, up to 1.5 tons	beats 90% · 2.23MZUHW18KCH21S2-ONon-ducted, up to 1.5 tons
Capacity retention at 5°F	beats 94% · 111%CU-XE9WKUANon-ducted, up to 1.5 tons	beats 85% · 89%MZUHW30KCH21S2-ODucted, 2.5–3 tons
HSPF2	beats 95% · 12.0CU-XE9WKUANon-ducted, up to 1.5 tons	beats 82% · 10.0MZUHW36KCH21S2-ONon-ducted, 2.5–3 tons
SEER2	beats 97% · 20.5CU-E9SD3UADucted, up to 1.5 tons	beats 83% · 24.0PUHW12KCH24S2-ONon-ducted, up to 1.5 tons
EER2	beats 97% · 16.1CU-XE9WKUANon-ducted, up to 1.5 tons	beats 84% · 12.5MZUHW30KCH21S2-ONon-ducted, 2.5–3 tons
Heating capacity at 5°F	beats 95% · 48,500 Btu/hCU-HE55YAHK6Ducted, 3.5–4.5 tons	beats 84% · 13,800 Btu/hMZUHW18KCH21S2-ONon-ducted, up to 1.5 tons

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Panasonic vs WILLIS heat pumps