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.

AIRTEMP and DIAMONDAIR 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, AIRTEMP scores higher on 3 of the 6 ratings.

AIRTEMP
DIAMONDAIR
Other ranked manufacturers

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

Average peer percentile, raw median and rank among ranked manufacturers
Rating	AIRTEMP	DIAMONDAIR
Efficiency index	45% (higher)median —	42% (higher)median —
COP at 5°F	32% (higher)median 1.81	30% (higher)median 1.82
Capacity retention at 5°F	65% (higher)median 77%	34% (higher)median 62%
HSPF2	37%median 8.5	42%median 7.5
SEER2	38%median 17.0	38%median 14.3
EER2	44%median 11.0	53%median 11.4
Heating capacity at 5°F	63% (higher)median 19,800 Btu/h	37% (higher)median 13,800 Btu/h
Outdoor models	25	25
AHRI certifications	58	74

Share of models meeting each standard

Percent of each manufacturer’s models with a qualifying certification
Standard	AIRTEMP	DIAMONDAIR
CEE 2025 Tier 1 (Split ASHP)	48%12 models	36%9 models
CEE 2026 Tier 1 (Split ASHP)	48%12 models	28%7 models
CEE Advanced Tier (Split ASHP)	0%0 models	0%0 models
Xcel Energy Colorado cold-climate ASHP (2025)	52%13 models	24%6 models
DOE Cold Climate Heat Pump Challenge	0%0 models	0%0 models
ENERGY STAR Cold Climate	32%8 models	0%0 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

AIRTEMP
DIAMONDAIR
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	AIRTEMP	DIAMONDAIR
Ducted, up to 1.5 tons	2 · index 31%	2 · index 59%
Ducted, 2 tons	3 · index 53%	2 · index 12%
Ducted, 2.5–3 tons	6 · index 52%	6 · index 40%
Ducted, 3.5–4.5 tons	4 · index 63%	6 · index 31%
Ducted, 5 tons and up	None	1 · index 19%
Non-ducted, up to 1.5 tons	8 · index 28%	7 · index 47%
Non-ducted, 2 tons	2 · index 57%	2 · index 40%
Non-ducted, 2.5–3 tons	5 · index 60%	2 · index 60%
Non-ducted, 3.5–4.5 tons	None	1 · index 40%

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	AIRTEMPCold-climate score, best model	DIAMONDAIRCold-climate score, best model
Ducted, up to 1.5 tons	35.6(50 is the typical model of its size class)GXH18(5.3)FMK4DH-11 of 2 models qualify · AHRI 210276818	52.0(50 is the typical model of its size class) (higher)DF18M2Z21 of 2 models qualify · AHRI 210857278
Ducted, 2 tons	50.1(50 is the typical model of its size class)GXH24(7.0)FMK4DH-11 of 2 models qualify · AHRI 210276819	None on this board (0 of 2 models qualify)
Ducted, 2.5–3 tons	55.3(50 is the typical model of its size class)GXH24-36MSK4DHwith ducted air handler GMH**-36MSK4DH14 of 7 models qualify · AHRI 206724409	57.4(50 is the typical model of its size class) (higher)DF30M2Z31 of 6 models qualify · AHRI 210857281
Ducted, 3.5–4.5 tons	58.1(50 is the typical model of its size class)GXH48-60MSK4DHwith ducted air handler GMH48-**MSK4DH11 of 4 models qualify · AHRI 206724410	None on this board (0 of 6 models qualify)
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	73.1(50 is the typical model of its size class)GXH18(5.3)FMK4DH-17 of 8 models qualify · AHRI 210276805	74.8(50 is the typical model of its size class) (higher)D2009SHO2with ductless indoor unit DF2009HMSI23 of 7 models qualify · AHRI 210857265
Non-ducted, 2 tons	76.1(50 is the typical model of its size class)GXH24(7.0)FMK4DH-12 of 2 models qualify · AHRI 210276806	86.1(50 is the typical model of its size class) (higher)D2024SHO2with ductless indoor unit DF2024CI21 of 2 models qualify · AHRI 210857272
Non-ducted, 2.5–3 tons	73.7(50 is the typical model of its size class) (higher)GXH42(12.3)FMK4DH-15 of 5 models qualify · AHRI 210276804	49.3(50 is the typical model of its size class)DF30M2Z31 of 2 models qualify · AHRI 210857280
Non-ducted, 3.5–4.5 tons	No models in this size class	None on this board (0 of 1 models qualify)

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	AIRTEMPAll-around score, best model	DIAMONDAIRAll-around score, best model
Ducted, up to 1.5 tons	31.2(50 is the typical model of its size class)GXH18(5.3)FMK4DH-11 of 2 models have all five ratings · AHRI 210276818	59.4(50 is the typical model of its size class) (higher)DF18M2Z21 of 2 models have all five ratings · AHRI 210857278
Ducted, 2 tons	60.8(50 is the typical model of its size class) (higher)GXH24-36MSK4DHwith ducted air handler GMH24-**MSK4DH12 of 3 models have all five ratings · AHRI 206724408	12.4(50 is the typical model of its size class)D1424HPG21 of 2 models have all five ratings · AHRI 212586117
Ducted, 2.5–3 tons	53.1(50 is the typical model of its size class)GXH30(8.8)FMK4DH-13 of 6 models have all five ratings · AHRI 210276820	71.5(50 is the typical model of its size class) (higher)DF30M2Z34 of 6 models have all five ratings · AHRI 210857281
Ducted, 3.5–4.5 tons	63.3(50 is the typical model of its size class) (higher)GXH48-60MSK4DHwith ducted air handler GMH48-**MSK4DH11 of 4 models have all five ratings · AHRI 206724410	52.1(50 is the typical model of its size class)DF55M2Z53 of 6 models have all five ratings · AHRI 210857287
Ducted, 5 tons and up	No models in this size class	19.3(50 is the typical model of its size class)D1460HPL21 of 1 models have all five ratings · AHRI 212586122
Non-ducted, up to 1.5 tons	58.0(50 is the typical model of its size class)GXH18(5.3)FMK4DH-18 of 8 models have all five ratings · AHRI 210276805	84.4(50 is the typical model of its size class) (higher)D2009SHO2with ductless indoor unit DF2009HMSI27 of 7 models have all five ratings · AHRI 210857265
Non-ducted, 2 tons	71.5(50 is the typical model of its size class) (higher)GXH24(7.0)FMK4DH-12 of 2 models have all five ratings · AHRI 210276806	70.7(50 is the typical model of its size class)D2024SHO2with ductless indoor unit DF2024HMSI22 of 2 models have all five ratings · AHRI 210857268
Non-ducted, 2.5–3 tons	70.2(50 is the typical model of its size class) (higher)GXH42(12.3)FMK4DH-15 of 5 models have all five ratings · AHRI 210276804	66.7(50 is the typical model of its size class)DF30M2Z32 of 2 models have all five ratings · AHRI 210857280
Non-ducted, 3.5–4.5 tons	No models in this size class	40.4(50 is the typical model of its size class)DF55M2Z51 of 1 models have all five ratings · AHRI 210857286

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	AIRTEMP	DIAMONDAIR
COP at 5°F	beats 89% · 2.21GXH18(5.3)FMK4DH-1Non-ducted, up to 1.5 tons	beats 78% · 2.10D1612HMSOFNon-ducted, up to 1.5 tons
Capacity retention at 5°F	beats 85% · 89%GXH30(8.8)FMK4DH-1Ducted, 2.5–3 tons	beats 92% · 103%D2024SHO2Non-ducted, 2 tons
HSPF2	beats 82% · 10.0GXH36(10.6)FMK4DH-1Non-ducted, 2.5–3 tons	beats 97% · 11.5D2024SHO2Non-ducted, 2 tons
SEER2	beats 83% · 24.0GXH12(3.5)LSK4DH2Non-ducted, up to 1.5 tons	beats 98% · 21.0DF30M2Z3Ducted, 2.5–3 tons
EER2	beats 84% · 12.5GXH30(8.8)FMK4DH-1Non-ducted, 2.5–3 tons	beats 95% · 15.8D2009SHO2Non-ducted, up to 1.5 tons
Heating capacity at 5°F	beats 86% · 14,500 Btu/hGXH18(5.3)LSK4DH2Non-ducted, up to 1.5 tons	beats 90% · 17,200 Btu/hD2018SHO2Non-ducted, up to 1.5 tons

More comparisons

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AIRTEMP vs DIAMONDAIR heat pumps