iFLOW vs WILLIS heat pumps

Measured against models of the same size and duct type, WILLIS scores higher on 4 of the 6 ratings. iFLOW has 14 outdoor models, WILLIS has 15 outdoor models. iFLOW and WILLIS have no QMID on file and are not ranked.

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CompareData as of Oct 11, 2026updated Oct 11, 2026 · sources

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.

iFLOW 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.

iFLOW
WILLIS
Other ranked manufacturers

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

Average peer percentile, raw median and rank among ranked manufacturers
Rating	iFLOW	WILLIS
Efficiency index	43%median —	51%median —
COP at 5°F	44% (higher)median 1.88	39% (higher)median 1.84
Capacity retention at 5°F	57%median 79%	64%median 76%
HSPF2	70% (higher)median 9.1	52% (higher)median 9.0
SEER2	36%median 15.2	55%median 21.0
EER2	21%median 10.0	46%median 12.0
Heating capacity at 5°F	63%median 29,000 Btu/h	68%median 13,600 Btu/h
Outdoor models	14	15
AHRI certifications	19	29

Share of models meeting each standard

Percent of each manufacturer’s models with a qualifying certification
Standard	iFLOW	WILLIS
CEE 2025 Tier 1 (Split ASHP)	14.3%2 models	86.7%13 models
CEE 2026 Tier 1 (Split ASHP)	14.3%2 models	80%12 models
CEE Advanced Tier (Split ASHP)	0%0 models	0%0 models
Xcel Energy Colorado cold-climate ASHP (2025)	50%7 models	86.7%13 models
DOE Cold Climate Heat Pump Challenge	0%0 models	0%0 models
ENERGY STAR Cold Climate	0%0 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 · 4 groups where both have models

iFLOW
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	iFLOW	WILLIS
Ducted, up to 1.5 tons	1 · index 52%	1 · index 32%
Ducted, 2 tons	2 · index 50%	1 · index 46%
Ducted, 2.5–3 tons	5 · index 43%	4 · index 51%
Ducted, 3.5–4.5 tons	6 · index 39%	2 · index 55%
Non-ducted, up to 1.5 tons	None	8 · index 44%
Non-ducted, 2 tons	None	1 · index 72%
Non-ducted, 2.5–3 tons	None	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	iFLOWCold-climate score, best model	WILLISCold-climate score, best model
Ducted, up to 1.5 tons	63.7(50 is the typical model of its size class) (higher)70HPIC18Awith ducted air handler 70C1824BA1 of 1 models qualify · AHRI 212546248	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)70HPIR24Awith ducted air handler 70C1824BA2 of 2 models qualify · AHRI 217729802	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)70HPIC36Awith ducted air handler 70C3036CA3 of 5 models qualify · AHRI 212546252	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	61.3(50 is the typical model of its size class) (higher)70HPIC45Awith ducted air handler 70C5460DA3 of 6 models qualify · AHRI 213279880	56.7(50 is the typical model of its size class)FLEX48/60KUHwith ducted air handler FLEXAH48/60K2 of 2 models qualify · AHRI 214797686
Non-ducted, up to 1.5 tons	No models in this size class	73.5(50 is the typical model of its size class)MZUHW18KCH21S2-O7 of 8 models qualify · AHRI 214810331
Non-ducted, 2 tons	No models in this size class	76.1(50 is the typical model of its size class)MZUHW24KCH21S2-O1 of 1 models qualify · AHRI 214810332
Non-ducted, 2.5–3 tons	No models in this size class	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	iFLOWAll-around score, best model	WILLISAll-around score, best model
Ducted, up to 1.5 tons	51.6(50 is the typical model of its size class) (higher)70HPIC18Awith ducted air handler 70C1824BA1 of 1 models have all five ratings · AHRI 212546248	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	53.2(50 is the typical model of its size class) (higher)70HPIC24Awith ducted air handler 70C1824AA2 of 2 models have all five ratings · AHRI 218029482	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	53.0(50 is the typical model of its size class)70HPIC36Awith ducted air handler 70C3036CA5 of 5 models have all five ratings · AHRI 212546252	53.1(50 is the typical model of its size class) (higher)MZUHW30KCH21S2-O4 of 4 models have all five ratings · AHRI 214810336
Ducted, 3.5–4.5 tons	49.8(50 is the typical model of its size class)70HPIC45Awith ducted air handler 70C5460DA6 of 6 models have all five ratings · AHRI 213279880	57.4(50 is the typical model of its size class) (higher)PRT60KUH2 of 2 models have all five ratings · AHRI 214137764
Non-ducted, up to 1.5 tons	No models in this size class	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	No models in this size class	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	No models in this size class	70.2(50 is the typical model of its size class)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	iFLOW	WILLIS
COP at 5°F	beats 76% · 2.2070HPIC18ADucted, up to 1.5 tons	beats 90% · 2.23MZUHW18KCH21S2-ONon-ducted, up to 1.5 tons
Capacity retention at 5°F	beats 78% · 85%70HPIC45ADucted, 3.5–4.5 tons	beats 85% · 89%MZUHW30KCH21S2-ODucted, 2.5–3 tons
HSPF2	beats 93% · 10.070HPIC36ADucted, 2.5–3 tons	beats 82% · 10.0MZUHW36KCH21S2-ONon-ducted, 2.5–3 tons
SEER2	beats 48% · 16.570HPIC24ADucted, 2 tons	beats 83% · 24.0PUHW12KCH24S2-ONon-ducted, up to 1.5 tons
EER2	beats 36% · 11.770HPIC18ADucted, up to 1.5 tons	beats 84% · 12.5MZUHW30KCH21S2-ONon-ducted, 2.5–3 tons
Heating capacity at 5°F	beats 89% · 46,500 Btu/h70HPIC45ADucted, 3.5–4.5 tons	beats 84% · 13,800 Btu/hMZUHW18KCH21S2-ONon-ducted, up to 1.5 tons

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