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SLIMAIR vs Viessmann: heat pump ratings compared

Against heat pumps of the same size and type, a typical SLIMAIR model beats 60% and a typical Viessmann model 60%. They are level.

Covers heat pumps sold new today (R-454B and R-32 refrigerant). See older R-410A models · Updated

SLIMAIR

60%

of similar heat pumps beaten by its typical model

Well above average

48 models listed

Viessmann

60%

of similar heat pumps beaten by its typical model

Well above average

43 models listed

Rating by ratingEach bar is the share of same-size, same-type heat pumps that a typical model beats, so the two brands compare fairly even if they make different sizes.
  • Efficiency on a 5°F dayCOP at 5°FSLIMAIR: Beats 60%Viessmann: Beats 53%
  • Heating power kept at 5°FCapacity at 5°F vs 47°FSLIMAIR: Beats 59%Viessmann: Beats 72%
  • Winter-long heating efficiencyHSPF2SLIMAIR: Beats 73%Viessmann: Beats 74%
  • Summer-long cooling efficiencySEER2SLIMAIR: Beats 61%Viessmann: Beats 59%
  • Hot-day cooling efficiencyEER2SLIMAIR: Beats 53%Viessmann: Beats 49%

Average (50%)Dashed outline: the other brand, for comparison

Want ranks, distributions per size class and cold-weather curves? Switch to Advanced

Rebate standards

Share of each brand’s models that meet the level. Programs can have other rules too.

  • CEE 2025

    SLIMAIR
    90%
    Viessmann
    84%

  • Xcel CC

    SLIMAIR
    77%
    Viessmann
    79%

  • CEE Advanced

    SLIMAIR
    2%
    Viessmann
    5%

  • ENERGY STAR CC

    SLIMAIR
    79%
    Viessmann
    70%

All-around best, ductless 3.5–4.5 tons

Balances heating (5°F output and efficiency, HSPF2) and cooling (SEER2, EER2), each rating against units their size.

Showing Ductless, 3.5–4.5 tons (39,000–56,999 Btu/h cooling). What size is my system?

SLIMAIR

  1. 1SHC6Z55AH2AGSLIMAIR4.5 tons · 51,000 Btu/h · DuctlessCold-climate pick, score 69.9Meets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    87% (Capacity at 5°F vs 47°F)
    Good
    Efficiency at 5°F
    2.00 (COP at 5°F)
    Below the middle
    Winter efficiency
    10.6 (HSPF2)
    Good
    Cooling efficiency
    21.4 (SEER2)
    Good
    Hot-day cooling
    12.0 (EER2)
    Good
    62.6score / 100Heating 58 · Cooling 67
  2. 2SHC6Z48AH2AGSLIMAIR4 tons · 45,000 Btu/h · DuctlessCold-climate pick, score 68.7Meets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    98% (Capacity at 5°F vs 47°F)
    Top 10%
    Efficiency at 5°F
    2.00 (COP at 5°F)
    Below the middle
    Winter efficiency
    10.2 (HSPF2)
    Good
    Cooling efficiency
    21.2 (SEER2)
    Good
    Hot-day cooling
    12.0 (EER2)
    Good
    62.6score / 100Heating 63 · Cooling 63
  3. 3SHC6Z48AC2AGSLIMAIR4 tons · 45,000 Btu/h · DuctlessCold-climate pick, score 60.1Meets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    78% (Capacity at 5°F vs 47°F)
    Below the middle
    Efficiency at 5°F
    2.10 (COP at 5°F)
    Great
    Winter efficiency
    10.3 (HSPF2)
    Good
    Cooling efficiency
    20.9 (SEER2)
    Below the middle
    Hot-day cooling
    11.9 (EER2)
    Good
    52.8score / 100Heating 60 · Cooling 46

Viessmann

  1. 1D5CMHAH48FAKViessmann4 tons · 47,000 Btu/h · DuctlessCold-climate pick, score 75.5Meets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    96% (Capacity at 5°F vs 47°F)
    Great
    Efficiency at 5°F
    2.00 (COP at 5°F)
    Below the middle
    Winter efficiency
    11.3 (HSPF2)
    Top 10%
    Cooling efficiency
    23.0 (SEER2)
    Great
    Hot-day cooling
    12.0 (EER2)
    Good
    76.7score / 100Heating 74 · Cooling 79
  2. 2D5CMHAH55FAKViessmann4.5 tons · 51,000 Btu/h · DuctlessCold-climate pick, score 66.0Meets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    85% (Capacity at 5°F vs 47°F)
    Good
    Efficiency at 5°F
    2.00 (COP at 5°F)
    Below the middle
    Winter efficiency
    10.5 (HSPF2)
    Good
    Cooling efficiency
    22.3 (SEER2)
    Great
    Hot-day cooling
    12.0 (EER2)
    Good
    64.2score / 100Heating 53 · Cooling 75
  3. 3D5CLHAH48AAKwith ductless indoor unit D5FLCAH48XAKViessmann4 tons · 48,000 Btu/h · DuctlessCold-climate pick, score 60.2Meets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    90% (Capacity at 5°F vs 47°F)
    Good
    Efficiency at 5°F
    1.96 (COP at 5°F)
    Below the middle
    Winter efficiency
    11.0 (HSPF2)
    Top 10%
    Cooling efficiency
    18.2 (SEER2)
    Below the middle
    Hot-day cooling
    10.0 (EER2)
    Below the middle
    38.2score / 100Heating 60 · Cooling 16

These are certified test ratings, not a recommendation for your home. The right size comes from a load calculation by a contractor.

Next steps

The advanced view adds ranks, both brands’ models inside every size class, standout models per rating and cold-weather curves.

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