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WILLIS heat pump efficiency: 29 outdoor models compared

WILLIS has 29 heat pump outdoor models certified with this refrigerant group, in 85 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 WILLIS makes. WILLIS 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 updated · sources

Outdoor models
29
AHRI certifications
85
Efficiency index
63%
Typical model vs same-size, same-type peers (42 models)
Meet CEE 2025
96.6%
28 models

How WILLIS 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.
WILLIS against every ranked manufacturerPeer scores, 0–100 · grey ticks: each ranked manufacturer · shaded: the middle half of WILLIS’s own modelsWILLIS is strongest on EER2 (its typical model beats 72% of comparable models) and weakest on COP at 5°F (44%).
  • WILLIS
  • Middle half of its models
  • Other ranked manufacturers
WILLIS

Source: AHRI Directory, NEEP · as of

Average peer percentile of WILLIS’s models
RatingBeats comparable modelsRankRaw median
Efficiency index42 models scored63%Not ranked—
COP at 5°F42 models scored44%Not ranked2.00
Capacity retention at 5°F42 models scored71%Not ranked90%
HSPF242 models scored50%Not ranked10.0
SEER242 models scored69%Not ranked21.0
EER242 models scored72%Not ranked12.5
Heating capacity at 5°F42 models scored65%Not ranked19,000 Btu/h

Standards met

Share of WILLIS’s models with at least one qualifying certification
StandardShareModels
CEE 2025 Tier 1 (Split ASHP)96.6%28
CEE 2026 Tier 1 (Split ASHP)96.6%28
CEE Advanced Tier (Split ASHP)10.3%3
Xcel Energy Colorado cold-climate ASHP (2025)96.6%28
DOE Cold Climate Heat Pump Challenge10.3%3
ENERGY STAR Cold Climate86.2%25

Sizes and duct types offered

Models per peer group, and how they score against the other models of that group.
WILLIS’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
  • WILLIS (median, middle 50%, 10th–90th)
  • 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 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

Source: AHRI Directory · as of

Share of comparable models beaten, per peer group
Size and duct typeModelsIndexCOP@5°FHSPF2SEER2
Ducted, up to 1.5 tons771%49%42%92%
Ducted, 2 tons567%35%64%69%
Ducted, 2.5–3 tons368%48%63%77%
Ducted, 3.5–4.5 tons377%55%76%82%
Non-ducted, up to 1.5 tons1358%47%47%62%
Non-ducted, 2 tons463%37%55%68%
Non-ducted, 2.5–3 tons647%34%31%52%
Non-ducted, 3.5–4.5 tons168%82%40%43%

Every WILLIS model in the market

WILLIS’s 42 models with a known size and duct type, over the shape of the whole catalog.
WILLIS models by size and ratingColoured: WILLIS · grey shapes: all 14,508 models · lines: catalog medians by size
  • WILLIS models
  • Ducted median by size
  • Non-ducted median by size
  • Every model at each size (width = count)
  • Standard threshold

Dots: 42 willis 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, sizeModels10th pct.25thMedian75th90th
Ducted, 0.5 tons8261.641.711.751.852.24
Ducted, 1 ton4071.801.902.052.412.45
Ducted, 1.5 tons9921.751.862.002.172.40
Ducted, 2 tons9991.751.862.002.182.30
Ducted, 2.5 tons1,0401.701.802.002.102.36
Ducted, 3 tons6961.801.902.002.102.42
Ducted, 3.5 tons8641.701.802.002.102.46
Ducted, 4 tons7271.801.862.002.122.40
Ducted, 4.5 tons6901.701.801.902.102.20
Ducted, 5 tons861.892.002.102.102.10
Non-ducted, 0.5 tons1,1861.751.801.902.002.22
Non-ducted, 1 ton1,3431.801.801.992.102.21
Non-ducted, 1.5 tons1,2611.801.802.002.102.31
Non-ducted, 2 tons7611.801.982.002.102.30
Non-ducted, 2.5 tons4031.801.852.002.002.10
Non-ducted, 3 tons4731.901.982.002.032.20
Non-ducted, 3.5 tons2802.002.002.002.052.10
Non-ducted, 4 tons2041.962.002.052.102.11
Non-ducted, 4.5 tons781.901.911.952.012.01
Non-ducted, 5 tons841.992.002.052.202.20

Source: AHRI Directory · as of

Top WILLIS 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 WILLIS 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 modelSize · typeCap. 5/47COP@5°FHSPF2Btu/h @5°FSEER2MeetsCombosAHRI ref.Compared withScore
1HW-COND36KWillis · Hi-PRO HDwith ducted air handler HW-AHU36K2.5 tons32,000 Btu/h · Ducted97%2.1510.531,00019.5CEE 25CEE 26XcelES CC1216772612Ducted, 2.5–3 tons87.9
2AUHW09KR32-OWILLIS · ULTIMAwith ductless indoor unit AUHW09KR32-I1 ton9,100 Btu/h · Non-ducted108%2.1111.211,50030.0CEE 25CEE 26CEE AdvXcelDOEES CC6217007963Non-ducted, up to 1.5 tons87.2
3FLEX60KUHR32Willis · FLEXX R32with ducted air handler FLEXAH60KR324.5 tons53,000 Btu/h · Ducted100%2.1010.554,00018.5CEE 25CEE 26CEE AdvXcelDOEES CC4216720958Ducted, 3.5–4.5 tons85.1
4FLEX48KUHR32Willis · FLEXX R32with ducted air handler FLEXAH48KR324 tons48,000 Btu/h · Ducted100%2.0010.048,00019.0CEE 25CEE 26XcelES CC1216720956Ducted, 3.5–4.5 tons78.9
5MZUHW36KR32-OWILLIS · MULTI HEAT3 tons36,000 Btu/h · Non-ducted100%2.1010.036,00021.0CEE 25CEE 26CEE AdvXcelDOEES CC3216772311Non-ducted, 2.5–3 tons77.2

All-around best

Top 5 WILLIS 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 modelSize · typeCap. 5/47COP@5°FHSPF2SEER2EER2MeetsCombosAHRI ref.Compared withScoreHeating halfCooling halfCold-climate score
1AUHW09KR32-OWILLIS · ULTIMAwith ductless indoor unit AUHW09KR32-I1 ton9,100 Btu/h · Non-ducted108%2.1111.230.016.8CEE 25CEE 26CEE AdvXcelDOEES CC6217007963Non-ducted, up to 1.5 tons92.687.297.987.2
2AUHW12KR32-OWILLIS · ULTIMAwith ductless indoor unit AUHW12KR32-I1 ton12,000 Btu/h · Non-ducted100%2.0010.029.515.2CEE 25CEE 26XcelES CC6217007964Non-ducted, up to 1.5 tons84.372.196.672.1
3PUHW09KR32-OWILLIS · Ductedwith ducted air handler WHEDT09K1 ton9,100 Btu/h · Ducted90%2.149.222.014.2CEE 25CEE 26XcelES CC6217560051Ducted, up to 1.5 tons83.669.997.469.9
4FLEX48KUHR32Willis · FLEXX R32with ducted air handler FLEXAH48KR32Also listed as FLEX60KUHR324 tons48,000 Btu/h · Ducted100%2.0010.019.012.0CEE 25CEE 26XcelES CC1216720956Ducted, 3.5–4.5 tons83.178.987.478.9
5HW-COND36KWillis · Hi-PRO HDwith ducted air handler HW-AHU36K2.5 tons32,000 Btu/h · Ducted97%2.1510.519.511.7CEE 25CEE 26XcelES CC1216772612Ducted, 2.5–3 tons82.387.976.787.9

Best model on each rating

WILLIS’s model with the highest peer percentile on each rating, ranked by that one rating only
RatingModelValueCompared withBeatsAHRI ref.
COP at 5°FMZUHW36KR32-O2.10Non-ducted, 2.5–3 tons88%216772311
Capacity retention at 5°FAUHW24KR32-O100%Non-ducted, 2 tons94%217007966
HSPF2HW-COND36K10.5Ducted, 2.5–3 tons96%216772612
SEER2AUHW18KR32-O24.5Ducted, up to 1.5 tons100%217560076
EER2AUHW09KR32-O16.8Non-ducted, up to 1.5 tons98%217007963
Heating capacity at 5°FFLEX60KUHR3254,000 Btu/hDucted, 3.5–4.5 tons98%216720958

All 29 WILLIS models in Explore

WILLIS 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.
WILLIS: 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 typeCold-climate pickCold-climate score, best modelAll-around bestAll-around score, best model
Ducted, up to 1.5 tons69.9(50 is the typical model of its size class)PUHW09KR32-Owith ducted air handler WHEDT09K7 of 7 models qualify · AHRI 21756005183.6(50 is the typical model of its size class)PUHW09KR32-Owith ducted air handler WHEDT09K7 of 7 models have all five ratings · AHRI 217560051
Ducted, 2 tons76.2(50 is the typical model of its size class)FLEX24KUHR32with ducted air handler FLEXAH24KR324 of 4 models qualify · AHRI 21672095373.1(50 is the typical model of its size class)FLEX24KUHR32with ducted air handler FLEXAH24KR325 of 5 models have all five ratings · AHRI 216720953
Ducted, 2.5–3 tons87.9(50 is the typical model of its size class)HW-COND36Kwith ducted air handler HW-AHU36K4 of 4 models qualify · AHRI 21677261282.3(50 is the typical model of its size class)HW-COND36Kwith ducted air handler HW-AHU36K3 of 3 models have all five ratings · AHRI 216772612
Ducted, 3.5–4.5 tons85.1(50 is the typical model of its size class)FLEX60KUHR32with ducted air handler FLEXAH60KR323 of 3 models qualify · AHRI 21672095883.1(50 is the typical model of its size class)FLEX48KUHR32with ducted air handler FLEXAH48KR32Also listed as FLEX60KUHR323 of 3 models have all five ratings · AHRI 216720956
Non-ducted, up to 1.5 tons87.2(50 is the typical model of its size class)AUHW09KR32-Owith ductless indoor unit AUHW09KR32-I13 of 13 models qualify · AHRI 21700796392.6(50 is the typical model of its size class)AUHW09KR32-Owith ductless indoor unit AUHW09KR32-I13 of 13 models have all five ratings · AHRI 217007963
Non-ducted, 2 tons70.3(50 is the typical model of its size class)PUHW24KR32-Owith ductless indoor unit PUHW24KR32-I3 of 4 models qualify · AHRI 21700796282.1(50 is the typical model of its size class)PUHW24KR32-Owith ductless indoor unit PUHW24KR32-I4 of 4 models have all five ratings · AHRI 217007962
Non-ducted, 2.5–3 tons77.2(50 is the typical model of its size class)MZUHW36KR32-O6 of 6 models qualify · AHRI 21677231170.5(50 is the typical model of its size class)MZUHW30KR32-O6 of 6 models have all five ratings · AHRI 216772310
Non-ducted, 3.5–4.5 tons66.5(50 is the typical model of its size class)MZUHW42KR32-O1 of 1 models qualify · AHRI 21677231267.7(50 is the typical model of its size class)MZUHW42KR32-O1 of 1 models have all five ratings · AHRI 216772312

All-around board, every manufacturer

Newest WILLIS certifications

By AHRI reference number; AHRI issues references in increasing order.
The 5 most recently certified WILLIS outdoor models
Outdoor modelSize · typeCOP@5°FCap. 5/47HSPF2SEER2MeetsCombosAHRI ref.
FLEX36KUHR32Willis · E Serieswith ducted air handler CC24R322 tons23,000 Btu/h · Ducted1.80100%8.516.0CEE 25CEE 26XcelES CC4217989300
FLEX60KUHR32Willis · E Serieswith ducted air handler CC48R324 tons47,000 Btu/h · Ducted1.85100%9.016.0CEE 25CEE 26CEE AdvXcelDOEES CC4217989298
CHW09KAR32-OWILLIS · Charmowith ductless indoor unit CHW09KAR32-I1 ton9,100 Btu/h · Non-ducted1.8676%8.820.5CEE 25CEE 26XcelES CC1217905255
CHW36KR32-OWILLIS · Charmowith ductless indoor unit CHW36KR32-I3 tons33,600 Btu/h · Non-ducted1.8072%8.521.0CEE 25CEE 26XcelES CC1217905254
CHW30KR32-OWILLIS · Charmowith ductless indoor unit CHW30KR32-I2.5 tons30,000 Btu/h · Non-ducted1.8077%9.022.0CEE 25CEE 26XcelES CC1217905253

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Compare WILLIS

Manufacturers of a similar size, side by side.

Compare with any manufacturer

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