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Air Tempo vs SUM X: heat pump ratings compared

Against heat pumps of the same size and type, a typical Air Tempo model beats 64% and a typical SUM X model 73%. SUM X rates higher overall.

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

Air Tempo

64%

of similar heat pumps beaten by its typical model

Well above average

6 models listed

SUM X

73%

of similar heat pumps beaten by its typical model

Well above average

6 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°FAir Tempo: Beats 18%SUM X: Beats 78%
  • Heating power kept at 5°FCapacity at 5°F vs 47°FAir Tempo: Beats 86%SUM X: Beats 80%
  • Winter-long heating efficiencyHSPF2Air Tempo: Beats 72%SUM X: Beats 70%
  • Summer-long cooling efficiencySEER2Air Tempo: Beats 78%SUM X: Beats 79%
  • Hot-day cooling efficiencyEER2Air Tempo: Beats 60%SUM X: Beats 61%

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

    Air Tempo
    100%
    SUM X
    100%

  • Xcel CC

    Air Tempo
    100%
    SUM X
    100%

  • CEE Advanced

    Air Tempo
    0%
    SUM X
    0%

  • ENERGY STAR CC

    Air Tempo
    100%
    SUM X
    100%

Top cold-climate picks, ductless up to 1.5 tons

Only units that keep at least 70% of their heat at 5°F, ranked on heat kept, efficiency at 5°F and seasonal efficiency (HSPF2), against units their size.

Showing Ductless, Up to 1.5 tons (under 21,000 Btu/h cooling). What size is my system?

Air Tempo

  1. 1ATCB12K454B-Owith ductless indoor unit ATCB12K454B-IAir TempoAlso listed as ATCB12K454B-O1 ton · 12,000 Btu/h · DuctlessKeeps 100% of its heat at 5°FMeets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    100% (Capacity at 5°F vs 47°F)
    Great
    Efficiency at 5°F
    1.80 (COP at 5°F)
    Below the middle
    Seasonal efficiency
    10.5 (HSPF2)
    Great
    62.1score / 100
  2. 2ATCB18K454B-Owith ductless indoor unit ATCB18K454B-IAir TempoAlso listed as ATCB18K454B-O1.5 tons · 18,000 Btu/h · DuctlessKeeps 99% of its heat at 5°FMeets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    99% (Capacity at 5°F vs 47°F)
    Great
    Efficiency at 5°F
    1.80 (COP at 5°F)
    Below the middle
    Seasonal efficiency
    10.0 (HSPF2)
    Good
    55.8score / 100

SUM X

  1. 1SM-12HSM2-CUwith ductless indoor unit SM-12HSM2-WUSUM X1 ton · 12,000 Btu/h · DuctlessKeeps 88% of its heat at 5°FMeets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    88% (Capacity at 5°F vs 47°F)
    Good
    Efficiency at 5°F
    2.00 (COP at 5°F)
    Good
    Seasonal efficiency
    9.5 (HSPF2)
    Below the middle
    60.1score / 100
  2. 2SM-18HSM2-CUwith ductless indoor unit SM-18HSM2-WUSUM X1.5 tons · 18,000 Btu/h · DuctlessKeeps 100% of its heat at 5°FMeets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    100% (Capacity at 5°F vs 47°F)
    Great
    Efficiency at 5°F
    1.90 (COP at 5°F)
    Below the middle
    Seasonal efficiency
    9.5 (HSPF2)
    Below the middle
    58.5score / 100

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.

Open the advanced view