ZERO heat pump efficiency: 119 outdoor models compared

ZERO has 119 heat pump outdoor models certified with this refrigerant group, in 164 AHRI-certified combinations. Each model is compared with models of the same size and duct type, so the scores below do not depend on which sizes ZERO makes. ZERO has no QMID (IRS Qualified Manufacturer ID) on file, so it is not ranked against other manufacturers.

New to heat pump ratings? The Simple view explains them in plain words →

ManufacturerData as of Oct 9, 2026updated Oct 10, 2026 · sources

Outdoor models: 119
AHRI certifications: 164
Efficiency index: 53%; Typical model vs same-size, same-type peers (130 models)
Meet CEE 2025: 70.6%; 84 models

How ZERO compares with comparable models

For each rating: the share of same-size, same-type models that a typical model of this manufacturer beats (50% is typical), its rank, and the raw median for context. Raw medians are not comparable across manufacturers that make different sizes.

ZERO against every ranked manufacturerPeer scores, 0–100 · grey ticks: each ranked manufacturer · shaded: the middle half of ZERO’s own modelsZERO is strongest on SEER2 (its typical model beats 58% of comparable models) and weakest on COP at 5°F (45%).

ZERO
Middle half of its models
Other ranked manufacturers

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

Average peer percentile of ZERO’s models
Rating	Beats comparable models	Rank	Raw median
Efficiency index130 models scored	53%	Not ranked	—
COP at 5°F130 models scored	45%	Not ranked	1.94
Capacity retention at 5°F130 models scored	52%	Not ranked	74%
HSPF2137 models scored	57%	Not ranked	9.5
SEER2137 models scored	58%	Not ranked	19.0
EER2137 models scored	48%	Not ranked	11.7
Heating capacity at 5°F130 models scored	55%	Not ranked	18,750 Btu/h

Standards met

Share of ZERO’s models with at least one qualifying certification
Standard	Share	Models
CEE 2025 Tier 1 (Split ASHP)	70.6%	84
CEE 2026 Tier 1 (Split ASHP)	69.7%	83
CEE Advanced Tier (Split ASHP)	0%	0
Xcel Energy Colorado cold-climate ASHP (2025)	64.7%	77
DOE Cold Climate Heat Pump Challenge	0%	0
ENERGY STAR Cold Climate	52.9%	63

Sizes and duct types offered

Models per peer group, and how they score against the other models of that group.

ZERO’s models inside each size and duct typeShape: every model of the group · blue: the middle half of this manufacturer’s models there, median dot, 10th–90th percentile line

ZERO (median, middle 50%, 10th–90th)
All models of the group

Source: AHRI Directory · as of Oct 9, 2026

Share of comparable models beaten, per peer group
Size and duct type	Models	Index	COP@5°F	HSPF2	SEER2
Ducted, up to 1.5 tons	7	68%	68%	59%	71%
Ducted, 2 tons	13	51%	36%	49%	54%
Ducted, 2.5–3 tons	20	54%	44%	56%	60%
Ducted, 3.5–4.5 tons	26	54%	44%	61%	58%
Ducted, 5 tons and up	2	64%	66%	82%	89%
Non-ducted, up to 1.5 tons	39	53%	42%	59%	59%
Non-ducted, 2 tons	9	50%	51%	58%	57%
Non-ducted, 2.5–3 tons	13	45%	45%	52%	51%
Non-ducted, 3.5–4.5 tons	6	52%	57%	49%	65%
Non-ducted, 5 tons and up	2	27%	42%	18%	16%

Every ZERO model in the market

ZERO’s 137 models with a known size and duct type, over the shape of the whole catalog.

ZERO models by size and ratingColoured: ZERO · grey shapes: all 14,508 models · lines: catalog medians by size

ZERO models
Ducted median by size
Non-ducted median by size
Every model at each size (width = count)
Standard threshold

Dots: 137 zero models, each through its representative certification, in the colour of the rating shown. The grey shapes count all 14,508 models, half a ton at a time.

Show the data as a table

COP at 5°F by size and duct type (every model, by rated cooling capacity)
Duct type, size	Models	10th pct.	25th	Median	75th	90th
Ducted, 0.5 tons	826	1.64	1.71	1.75	1.85	2.24
Ducted, 1 ton	407	1.80	1.90	2.05	2.41	2.45
Ducted, 1.5 tons	992	1.75	1.86	2.00	2.17	2.40
Ducted, 2 tons	999	1.75	1.86	2.00	2.18	2.30
Ducted, 2.5 tons	1,040	1.70	1.80	2.00	2.10	2.36
Ducted, 3 tons	696	1.80	1.90	2.00	2.10	2.42
Ducted, 3.5 tons	864	1.70	1.80	2.00	2.10	2.46
Ducted, 4 tons	727	1.80	1.86	2.00	2.12	2.40
Ducted, 4.5 tons	690	1.70	1.80	1.90	2.10	2.20
Ducted, 5 tons	86	1.89	2.00	2.10	2.10	2.10
Non-ducted, 0.5 tons	1,186	1.75	1.80	1.90	2.00	2.22
Non-ducted, 1 ton	1,343	1.80	1.80	1.99	2.10	2.21
Non-ducted, 1.5 tons	1,261	1.80	1.80	2.00	2.10	2.31
Non-ducted, 2 tons	761	1.80	1.98	2.00	2.10	2.30
Non-ducted, 2.5 tons	403	1.80	1.85	2.00	2.00	2.10
Non-ducted, 3 tons	473	1.90	1.98	2.00	2.03	2.20
Non-ducted, 3.5 tons	280	2.00	2.00	2.00	2.05	2.10
Non-ducted, 4 tons	204	1.96	2.00	2.05	2.10	2.11
Non-ducted, 4.5 tons	78	1.90	1.91	1.95	2.01	2.01
Non-ducted, 5 tons	84	1.99	2.00	2.05	2.20	2.20

Source: AHRI Directory · as of Oct 9, 2026

Top ZERO models

Its top five cold-climate picks and its top five all-around models across sizes (both scores compare each model with models of its own size and duct type, so sizes compare), then, on each single rating, the model that beats the largest share of comparable models.

Cold-climate picks

Top 5 ZERO cold-climate picks across sizes. 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.
# · Outdoor model	Size · type	Cap. 5/47	COP@5°F	HSPF2	Btu/h @5°F	SEER2	Meets	Combos	AHRI ref.	Compared with	Score
1ZMSB-09HV-USHHR2-OZERO · ZMSB Serieswith ductless indoor unit ZMSB-09HV-USHHR2-I	1 ton9,000 Btu/h · Non-ducted	82%	2.33	13.0	8,200	24.6	CEE 25CEE 26XcelES CC	3	216097679	Non-ducted, up to 1.5 tons	85.9
2Z4SOV-48HDMB-USHHZERO · Z4S Series	4 tons47,000 Btu/h · Ducted	100%	2.00	11.0	48,000	20.4	CEE 25CEE 26XcelES CC	3	217752809	Ducted, 3.5–4.5 tons	82.7
3Z4SOV-36HDMB-USHHZERO · Z4S Series	3 tons36,000 Btu/h · Ducted	106%	2.00	10.4	38,000	19.4	CEE 25CEE 26XcelES CC	3	217752806	Ducted, 2.5–3 tons	82.5
4Z4SOV-53HDMB-USHHZERO · Z4S Series	4.5 tons53,000 Btu/h · Ducted	87%	2.10	10.7	48,000	20.0	CEE 25CEE 26XcelES CC	3	217752812	Ducted, 3.5–4.5 tons	81.2
5ZMSB-18HV-USHHCR2-OZERO · ZMSB Serieswith ductless indoor unit ZMSB-18HV-USHHCR2-I	1.5 tons18,000 Btu/h · Non-ducted	100%	2.00	10.8	18,000	21.7	CEE 25CEE 26XcelES CC	1	216097675	Non-ducted, up to 1.5 tons	78.3

All-around best

Top 5 ZERO models on the all-around score across sizes. 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.
# · Outdoor model	Size · type	Cap. 5/47	COP@5°F	HSPF2	SEER2	EER2	Meets	Combos	AHRI ref.	Compared with	Score	Heating half	Cooling half	Cold-climate score
1ZMSB-09HV-USHHR2-OZERO · ZMSB Serieswith ductless indoor unit ZMSB-09HV-USHHR2-I	1 ton9,000 Btu/h · Non-ducted	82%	2.33	13.0	24.6	14.7	CEE 25CEE 26XcelES CC	3	216097679	Non-ducted, up to 1.5 tons	86.7	85.9	87.4	85.9
2Z4SOV-48HDMB-USZERO · Z4S SeriesAlso listed as Z6SOV-48HDMB-US	4 tons45,000 Btu/h · Ducted	81%	2.10	10.6	20.4	12.0	CEE 25CEE 26XcelES CC	3	217138410	Ducted, 3.5–4.5 tons	85.1	77.9	92.3	77.9
3Z4SOV-48HDMB-USHHZERO · Z4S Series	4 tons47,000 Btu/h · Ducted	100%	2.00	11.0	20.4	11.7	CEE 25CEE 26XcelES CC	3	217752809	Ducted, 3.5–4.5 tons	83.9	82.7	85.1	82.7
4Z4SOV-36HDMB-USHHZERO · Z4S Series	3 tons36,000 Btu/h · Ducted	106%	2.00	10.4	19.4	12.0	CEE 25CEE 26XcelES CC	3	217752806	Ducted, 2.5–3 tons	83.6	82.5	84.8	82.5
5Z4SOV-53HDMB-USHHZERO · Z4S Series	4.5 tons53,000 Btu/h · Ducted	87%	2.10	10.7	20.0	11.7	CEE 25CEE 26XcelES CC	3	217752812	Ducted, 3.5–4.5 tons	82.0	81.2	82.8	81.2

Best model on each rating

ZERO’s model with the highest peer percentile on each rating, ranked by that one rating only
Rating	Model	Value	Compared with	Beats	AHRI ref.
COP at 5°F	ZOU-42HDCA-S14	2.80	Ducted, 3.5–4.5 tons	99%	218617686
Capacity retention at 5°F	ZRRV07HPBYFC-18SAlso listed as ZPRVO7HPBYFC-18S, ZPRV07HPBYFC-18S	103%	Ducted, 2 tons	97%	217904930
HSPF2	Z4SOV-48HDMB-USHH	11.0	Ducted, 3.5–4.5 tons	99%	217752809
SEER2	Z3SOV-27HDTB-US	22.0	Ducted, 2.5–3 tons	99%	216723125
EER2	ZOV-24HDGB	13.3	Ducted, 2 tons	93%	217619841
Heating capacity at 5°F	ZSOVA-36HDMB-USHH	39,000 Btu/h	Ducted, 2.5–3 tons	97%	216980498

All 119 ZERO models in Explore

ZERO size class by size class: cold-climate and all-around

Its best model on each board in every size and duct type it makes. Both scores are 0–100 against every model of that size class (the line on each bar is 50, the typical model there). Cold-climate picks must keep at least 70% of their heat at 5°F; the all-around score needs all five ratings and has no such bar.

ZERO: best cold-climate pick and best all-around model per size and duct type, with how many of its models are on each board (top 5 and 5 per class are in the snapshot)
Size and duct type	Cold-climate pickCold-climate score, best model	All-around bestAll-around score, best model
Ducted, up to 1.5 tons	72.6(50 is the typical model of its size class)Z4SOV-18HDMB-USAlso listed as Z3SOV-18HDMB-US5 of 7 models qualify · AHRI 217138401	77.4(50 is the typical model of its size class)Z4SOV-18HDMB-USHH6 of 7 models have all five ratings · AHRI 217752800
Ducted, 2 tons	70.4(50 is the typical model of its size class)ZRRV07HPBYFC-18SAlso listed as ZPRVO7HPBYFC-18S, ZPRV07HPBYFC-18S11 of 13 models qualify · AHRI 217904930	79.6(50 is the typical model of its size class)ZOV-24HDGBwith ducted air handler ZAV-24HDGB12 of 13 models have all five ratings · AHRI 217619841
Ducted, 2.5–3 tons	82.5(50 is the typical model of its size class)Z4SOV-36HDMB-USHH13 of 20 models qualify · AHRI 217752806	83.6(50 is the typical model of its size class)Z4SOV-36HDMB-USHH18 of 20 models have all five ratings · AHRI 217752806
Ducted, 3.5–4.5 tons	82.7(50 is the typical model of its size class)Z4SOV-48HDMB-USHH19 of 26 models qualify · AHRI 217752809	85.1(50 is the typical model of its size class)Z4SOV-48HDMB-USAlso listed as Z6SOV-48HDMB-US23 of 26 models have all five ratings · AHRI 217138410
Ducted, 5 tons and up	None on this board (0 of 2 models qualify)	64.7(50 is the typical model of its size class)Z4SOV-60HDMB-US2 of 2 models have all five ratings · AHRI 217138413
Non-ducted, up to 1.5 tons	85.9(50 is the typical model of its size class)ZMSB-09HV-USHHR2-Owith ductless indoor unit ZMSB-09HV-USHHR2-I31 of 39 models qualify · AHRI 216097679	86.7(50 is the typical model of its size class)ZMSB-09HV-USHHR2-Owith ductless indoor unit ZMSB-09HV-USHHR2-I39 of 39 models have all five ratings · AHRI 216097679
Non-ducted, 2 tons	77.2(50 is the typical model of its size class)ZMSB-24HV-USHHCR2-Owith ductless indoor unit ZMSB-24HV-USHHCR2-I7 of 9 models qualify · AHRI 216097676	74.3(50 is the typical model of its size class)ZMSB-24HV-USHHR2-Owith ductless indoor unit ZMSB-24HV-USHHR2-I9 of 9 models have all five ratings · AHRI 216097682
Non-ducted, 2.5–3 tons	72.6(50 is the typical model of its size class)Z4SOV-36HDMB-USHH9 of 13 models qualify · AHRI 217752807	66.3(50 is the typical model of its size class)Z4SOV-36HDMB-USHH13 of 13 models have all five ratings · AHRI 217752805
Non-ducted, 3.5–4.5 tons	69.9(50 is the typical model of its size class)Z4SOV-53HDMB-USHH6 of 6 models qualify · AHRI 217752813	62.6(50 is the typical model of its size class)Z4SOV-53HDMB-USHH6 of 6 models have all five ratings · AHRI 217752811
Non-ducted, 5 tons and up	None on this board (0 of 2 models qualify)	32.5(50 is the typical model of its size class)Z4SOV-60HDMB-USAlso listed as Z6SOV-60HDMB-US2 of 2 models have all five ratings · AHRI 217138412

All-around board, every manufacturer

Newest ZERO certifications

By AHRI reference number; AHRI issues references in increasing order.

The 5 most recently certified ZERO outdoor models
Outdoor model	Size · type	COP@5°F	Cap. 5/47	HSPF2	SEER2	Meets	Combos	AHRI ref.
Z5SOV-42HDTA-US-OZERO · Z-MAX US R32 Hyper Heat Series	3.5 tons42,000 Btu/h · Non-ducted	2.00	74%	10.0	24.0	CEE 25CEE 26XcelES CC	1	218665169
Z4SOV-36HDTA-US-OZERO · Z-MAX US R32 Hyper Heat Series	3 tons38,000 Btu/h · Non-ducted	2.00	74%	10.0	23.0	CEE 25CEE 26XcelES CC	1	218665168
Z3SOV-27HDTA-US-OZERO · Z-MAX US R32 Hyper Heat Series	2.5 tons28,000 Btu/h · Non-ducted	2.00	75%	10.0	22.0	CEE 25CEE 26XcelES CC	1	218665166
Z2SOV-18HDTA-US-OZERO · Z-MAX US R32 Hyper Heat Series	1.5 tons18,000 Btu/h · Non-ducted	2.00	78%	10.0	25.0	CEE 25CEE 26XcelES CC	1	218665165
ZMSB-24HVT-USR1-S23-OZERO · Z-MAX US R32 Hyper Heat Serieswith ductless indoor unit ZMSB-24HVT-USR1-S23-I	2 tons23,000 Btu/h · Non-ducted	2.10	73%	10.0	23.0	CEE 25CEE 26XcelES CC	1	218665163

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Compare ZERO

Manufacturers of a similar size, side by side.

Compare with any manufacturer

ZERO includes these brand names as listed in AHRI: ZERO. Standards are checked against published thresholds; program rules beyond ratings are not checked.