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.

Nortek Global HVAC and ZERO 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, ZERO scores higher on 3 of the 6 ratings.

Nortek Global HVAC
ZERO
Other ranked manufacturers

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

Average peer percentile, raw median and rank among ranked manufacturers
Rating	Nortek Global HVAC	ZERO
Efficiency index	51% (higher)median — · 20th ranked	49% (higher)median —
COP at 5°F	44%median 1.85 · 23rd ranked	48%median 1.89
Capacity retention at 5°F	64% (higher)median 80% · 4th ranked	43% (higher)median 70%
HSPF2	38%median 8.2 · 22nd ranked	46%median 8.6
SEER2	39%median 16.5 · 22nd ranked	53%median 19.0
EER2	46%median 11.0 · 21st ranked	46%median 11.0
Heating capacity at 5°F	56% (higher)median 14,500 Btu/h · 10th ranked	44% (higher)median 11,700 Btu/h
Outdoor models	75	69
AHRI certifications	280	89

Share of models meeting each standard

Percent of each manufacturer’s models with a qualifying certification
Standard	Nortek Global HVAC	ZERO
CEE 2025 Tier 1 (Split ASHP)	38.7%29 models	59.4%41 models
CEE 2026 Tier 1 (Split ASHP)	38.7%29 models	55.1%38 models
CEE Advanced Tier (Split ASHP)	0%0 models	0%0 models
Xcel Energy Colorado cold-climate ASHP (2025)	41.3%31 models	47.8%33 models
DOE Cold Climate Heat Pump Challenge	0%0 models	0%0 models
ENERGY STAR Cold Climate	29.3%22 models	24.6%17 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

Nortek Global HVAC
ZERO
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	Nortek Global HVAC	ZERO
Ducted, up to 1.5 tons	10 · index 47%	2 · index 59%
Ducted, 2 tons	7 · index 52%	5 · index 69%
Ducted, 2.5–3 tons	20 · index 55%	7 · index 57%
Ducted, 3.5–4.5 tons	13 · index 58%	9 · index 63%
Ducted, 5 tons and up	None	1 · index 57%
Non-ducted, up to 1.5 tons	23 · index 47%	33 · index 48%
Non-ducted, 2 tons	7 · index 53%	9 · index 49%
Non-ducted, 2.5–3 tons	10 · index 56%	8 · index 39%
Non-ducted, 3.5–4.5 tons	1 · index 45%	3 · index 50%

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	Nortek Global HVACCold-climate score, best model	ZEROCold-climate score, best model
Ducted, up to 1.5 tons	55.9(50 is the typical model of its size class) (higher)WHU09SZA21Swith ducted air handler WHU09DHA21S5 of 10 models qualify · AHRI 207237540	52.0(50 is the typical model of its size class)Z3SOV-18HDM-US1 of 2 models qualify · AHRI 214723150
Ducted, 2 tons	68.1(50 is the typical model of its size class)WHM24SZA21Swith ducted air handler D(A,C,E)24D44+TDR4 of 6 models qualify · AHRI 214640590	80.3(50 is the typical model of its size class) (higher)ZSOV-24HDM-USwith ducted air handler ZDV-24HDM-US2 of 5 models qualify · AHRI 212928560
Ducted, 2.5–3 tons	78.1(50 is the typical model of its size class) (higher)WHU36SZA21Swith ducted air handler WHU36DHA21S7 of 21 models qualify · AHRI 207237544	57.4(50 is the typical model of its size class)Z3SOV-27HDM-US1 of 7 models qualify · AHRI 213732663
Ducted, 3.5–4.5 tons	73.0(50 is the typical model of its size class)WHM60SZA21Swith ducted air handler D(A,C,E)60B44+TDR4 of 13 models qualify · AHRI 214640596	74.9(50 is the typical model of its size class) (higher)Z5SOV-48HDM-US1 of 9 models qualify · AHRI 213732669
Ducted, 5 tons and up	No models in this size class	None on this board (0 of 1 models qualify)
Non-ducted, up to 1.5 tons	78.4(50 is the typical model of its size class)WHU09SZA21Swith ductless indoor unit WHU09CTA21S17 of 23 models qualify · AHRI 207237535	86.0(50 is the typical model of its size class) (higher)ZMSB-09HV-USHHwith ductless indoor unit ZMSB-09HV-USHH24 of 33 models qualify · AHRI 213917748
Non-ducted, 2 tons	76.1(50 is the typical model of its size class) (higher)GXH24(7.0)FMK4DH-15 of 7 models qualify · AHRI 210276801	74.2(50 is the typical model of its size class)ZSOV-24HDM-USwith ductless indoor unit ZEV-24HDM-US4 of 9 models qualify · AHRI 212928564
Non-ducted, 2.5–3 tons	77.2(50 is the typical model of its size class) (higher)WHU36SZA21Swith ductless indoor unit WHU36CTA21S7 of 10 models qualify · AHRI 207237539	49.3(50 is the typical model of its size class)Z3SOV-27HDM-US1 of 8 models qualify · AHRI 213732662
Non-ducted, 3.5–4.5 tons	42.0(50 is the typical model of its size class)WHP42M5A21S1 of 1 models qualify · AHRI 208404161	80.5(50 is the typical model of its size class) (higher)Z5SOV-48HDM-US2 of 3 models qualify · AHRI 213732668

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	Nortek Global HVACAll-around score, best model	ZEROAll-around score, best model
Ducted, up to 1.5 tons	57.7(50 is the typical model of its size class)WHU09SZA21Swith ducted air handler WHU09DHA21S5 of 10 models have all five ratings · AHRI 207237540	59.4(50 is the typical model of its size class) (higher)Z3SOV-18HDM-US1 of 2 models have all five ratings · AHRI 214723150
Ducted, 2 tons	71.6(50 is the typical model of its size class)WHP24M3A21S6 of 7 models have all five ratings · AHRI 208404156	83.8(50 is the typical model of its size class) (higher)ZSOV-24HDM-USwith ducted air handler ZDV-24HDM-US2 of 5 models have all five ratings · AHRI 212928560
Ducted, 2.5–3 tons	78.6(50 is the typical model of its size class) (higher)WHP36M4A21S7 of 20 models have all five ratings · AHRI 208404158	71.5(50 is the typical model of its size class)Z3SOV-27HDM-US3 of 7 models have all five ratings · AHRI 213732663
Ducted, 3.5–4.5 tons	65.5(50 is the typical model of its size class)WHM48SZA21Swith ducted air handler DC61A44-245R4 of 13 models have all five ratings · AHRI 213886028	82.0(50 is the typical model of its size class) (higher)Z5SOV-48HDM-US2 of 9 models have all five ratings · AHRI 213732669
Ducted, 5 tons and up	No models in this size class	57.1(50 is the typical model of its size class)ZSOV-60HDM-USwith ducted air handler ZDV-60HDM-US1 of 1 models have all five ratings · AHRI 212928563
Non-ducted, up to 1.5 tons	85.4(50 is the typical model of its size class)WHZ09SZA21Swith ductless indoor unit WHZ09WMA21S19 of 24 models have all five ratings · AHRI 207337194	86.7(50 is the typical model of its size class) (higher)ZMSB-09HV-USHHwith ductless indoor unit ZMSB-09HV-USHH33 of 33 models have all five ratings · AHRI 213917748
Non-ducted, 2 tons	71.5(50 is the typical model of its size class)GXH24(7.0)FMK4DH-16 of 7 models have all five ratings · AHRI 210276801	72.0(50 is the typical model of its size class) (higher)ZSOV-24HDM-USwith ductless indoor unit ZEV-24HDM-US9 of 9 models have all five ratings · AHRI 212928564
Non-ducted, 2.5–3 tons	70.2(50 is the typical model of its size class) (higher)GXH42(12.3)FMK4DH-18 of 10 models have all five ratings · AHRI 210276799	66.7(50 is the typical model of its size class)Z3SOV-27HDM-US8 of 8 models have all five ratings · AHRI 213732662
Non-ducted, 3.5–4.5 tons	No models in this size class	73.8(50 is the typical model of its size class)Z5SOV-48HDM-US3 of 3 models have all five ratings · AHRI 213732668

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	Nortek Global HVAC	ZERO
COP at 5°F	beats 96% · 2.28WHU36SZA21SNon-ducted, 2.5–3 tons	beats 96% · 2.22ZMSB-24HV-USHHNon-ducted, 2 tons
Capacity retention at 5°F	beats 99% · 113%WHP36M4A21SNon-ducted, 2.5–3 tons	beats 84% · 87%Z5SOV-48HDM-USDucted, 3.5–4.5 tons
HSPF2	beats 83% · 9.5WHU36SZA21SDucted, 2.5–3 tons	beats 98% · 11.2ZSOV-24HDM-USDucted, 2 tons
SEER2	beats 96% · 27.5WHZ09SZA21SNon-ducted, up to 1.5 tons	beats 99% · 20.9Z5SOV-48HDM-USDucted, 3.5–4.5 tons
EER2	beats 93% · 15.5WHZ09SZA21SNon-ducted, up to 1.5 tons	beats 95% · 15.8ZMSB-09HV-USHHCAlso listed as ZMSB-09HV-USHHC-ONon-ducted, up to 1.5 tons
Heating capacity at 5°F	beats 92% · 18,000 Btu/hWHP18M2A21SNon-ducted, up to 1.5 tons	beats 90% · 17,200 Btu/hZMSB-18HV-USHHCAlso listed as ZMSB-18HV-USHHC-ONon-ducted, up to 1.5 tons

More comparisons

Pick any two manufacturers

Nortek Global HVAC vs ZERO heat pumps