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DiamondAir vs ZEPHYR heat pumps

Measured against models of the same size and duct type, ZEPHYR scores higher on 3 of the 6 ratings. DiamondAir has 7 outdoor models, ZEPHYR has 23 outdoor models. DiamondAir and ZEPHYR have no QMID on file and are not ranked.

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CompareData as of updated · 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.
DiamondAir and ZEPHYR 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, ZEPHYR scores higher on 3 of the 6 ratings.
  • DiamondAir
  • ZEPHYR
  • Other ranked manufacturers
DiamondA…ZEPHYR

Source: AHRI Directory, NEEP · as of

Average peer percentile, raw median and rank among ranked manufacturers
RatingDiamondAirZEPHYR
Efficiency index—median —63%median —
COP at 5°F—median —57%median 2.00
Capacity retention at 5°F—median —64%median 80%
HSPF226%median 7.559%median 10.0
SEER221%median 14.367%median 22.0
EER260%median 11.765%median 12.3
Heating capacity at 5°F—median —57%median 13,400 Btu/h
Outdoor models723
AHRI certifications749

Share of models meeting each standard

Percent of each manufacturer’s models with a qualifying certification
StandardDiamondAirZEPHYR
CEE 2025 Tier 1 (Split ASHP)0%0 models100%23 models
CEE 2026 Tier 1 (Split ASHP)0%0 models95.7%22 models
CEE Advanced Tier (Split ASHP)0%0 models8.7%2 models
Xcel Energy Colorado cold-climate ASHP (2025)0%0 models82.6%19 models
DOE Cold Climate Heat Pump Challenge0%0 models8.7%2 models
ENERGY STAR Cold Climate0%0 models73.9%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 · 4 groups where both have models
  • DiamondAir
  • ZEPHYR
  • All models of the group
Ducted, up to 1.5 tons1.901,783 modelsDucted, 2 tons2.001,090 modelsDucted, 2.5–3 tons2.001,909 modelsDucted, 3.5–4.5 tons2.002,224 modelsDucted, 5 tons and up2.00321 modelsNon-ducted, up to 1.5 tons1.953,455 modelsNon-ducted, 2 tons2.00863 modelsNon-ducted, 2.5–3 tons2.001,106 modelsNon-ducted, 3.5–4.5 tons2.00564 modelsmedian

Raw ratings are only placed side by side within one size and duct type, where they are comparable.

Source: AHRI Directory · as of

Models per peer group · efficiency index within the group
Size and duct typeDiamondAirZEPHYR
Ducted, up to 1.5 tons1 · index —1 · index 65%
Ducted, 2 tons1 · index —1 · index 80%
Ducted, 2.5–3 tons3 · index —3 · index 71%
Ducted, 3.5–4.5 tons2 · index —2 · index 71%
Ducted, 5 tons and upNone1 · index 81%
Non-ducted, up to 1.5 tonsNone14 · index 62%
Non-ducted, 2 tonsNone2 · index 48%
Non-ducted, 2.5–3 tonsNone2 · index 63%
Non-ducted, 3.5–4.5 tonsNone1 · index 44%

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 typeDiamondAirCold-climate score, best modelZEPHYRCold-climate score, best model
Ducted, up to 1.5 tonsNone on this board (0 of 1 models qualify)66.2(50 is the typical model of its size class)ZE-518M2251 of 1 models qualify · AHRI 216684162
Ducted, 2 tonsNone on this board (0 of 1 models qualify)82.1(50 is the typical model of its size class)ZE-624HPAwith ducted air handler AH-624A1 of 1 models qualify · AHRI 215381145
Ducted, 2.5–3 tonsNone on this board (0 of 3 models qualify)87.9(50 is the typical model of its size class)ZE-636HPAwith ducted air handler AH-636A3 of 3 models qualify · AHRI 215381146
Ducted, 3.5–4.5 tonsNone on this board (0 of 2 models qualify)77.3(50 is the typical model of its size class)ZE-648HPAwith ducted air handler AH-648A2 of 2 models qualify · AHRI 215381147
Ducted, 5 tons and upNo models in this size class88.7(50 is the typical model of its size class)ZE-660HPAwith ducted air handler AH-660A1 of 1 models qualify · AHRI 215381148
Non-ducted, up to 1.5 tonsNo models in this size class89.7(50 is the typical model of its size class)ZE-09UB32Owith ductless indoor unit ZE-09UB32I10 of 14 models qualify · AHRI 217596868
Non-ducted, 2 tonsNo models in this size class54.1(50 is the typical model of its size class)ZE-24CB25Owith ductless indoor unit ZE-24CB25AI2 of 2 models qualify · AHRI 218046582
Non-ducted, 2.5–3 tonsNo models in this size class53.7(50 is the typical model of its size class)ZE-536M4252 of 2 models qualify · AHRI 216684171
Non-ducted, 3.5–4.5 tonsNo models in this size class16.4(50 is the typical model of its size class)ZE-542M5251 of 1 models qualify · AHRI 216684168

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 typeDiamondAirAll-around score, best modelZEPHYRAll-around score, best model
Ducted, up to 1.5 tonsNone on this board (0 of 1 models have all five ratings)64.6(50 is the typical model of its size class)ZE-518M2251 of 1 models have all five ratings · AHRI 216684162
Ducted, 2 tonsNone on this board (0 of 1 models have all five ratings)79.5(50 is the typical model of its size class)ZE-624HPAwith ducted air handler AH-624A1 of 1 models have all five ratings · AHRI 215381145
Ducted, 2.5–3 tonsNone on this board (0 of 3 models have all five ratings)82.3(50 is the typical model of its size class)ZE-636HPAwith ducted air handler AH-636A3 of 3 models have all five ratings · AHRI 215381146
Ducted, 3.5–4.5 tonsNone on this board (0 of 2 models have all five ratings)82.3(50 is the typical model of its size class)ZE-648HPAwith ducted air handler AH-648A2 of 2 models have all five ratings · AHRI 215381147
Ducted, 5 tons and upNo models in this size class81.1(50 is the typical model of its size class)ZE-660HPAwith ducted air handler AH-660A1 of 1 models have all five ratings · AHRI 215381148
Non-ducted, up to 1.5 tonsNo models in this size class94.5(50 is the typical model of its size class)ZE-09UB32Owith ductless indoor unit ZE-09UB32I14 of 14 models have all five ratings · AHRI 217596868
Non-ducted, 2 tonsNo models in this size class61.3(50 is the typical model of its size class)ZE-24CB25Owith ductless indoor unit ZE-24CB25AI2 of 2 models have all five ratings · AHRI 218046582
Non-ducted, 2.5–3 tonsNo models in this size class64.2(50 is the typical model of its size class)ZE-527M3252 of 2 models have all five ratings · AHRI 216684164
Non-ducted, 3.5–4.5 tonsNo models in this size class43.7(50 is the typical model of its size class)ZE-542M5251 of 1 models have all five ratings · AHRI 216684168

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
RatingDiamondAirZEPHYR
COP at 5°F—beats 100% · 2.53ZE-18CB22ONon-ducted, up to 1.5 tons
Capacity retention at 5°F—beats 94% · 75%ZE-660HPADucted, 5 tons and up
HSPF2beats 27% · 7.5D1448HCL32ADucted, 3.5–4.5 tonsbeats 96% · 10.5ZE-636HPADucted, 2.5–3 tons
SEER2beats 22% · 14.3D1448HCL32ADucted, 3.5–4.5 tonsbeats 99% · 32.0ZE-09UB32ONon-ducted, up to 1.5 tons
EER2beats 67% · 11.7D1448HCL32ADucted, 3.5–4.5 tonsbeats 100% · 18.4ZE-09UB32ONon-ducted, up to 1.5 tons
Heating capacity at 5°F—beats 93% · 18,000 Btu/hZE-18CB25ONon-ducted, up to 1.5 tons

More comparisons

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