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IWAE vs ZEPHYR: heat pump ratings compared

Against heat pumps of the same size and type, a typical IWAE model beats 52% and a typical ZEPHYR model 63%. ZEPHYR rates higher overall.

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

IWAE

52%

of similar heat pumps beaten by its typical model

About average

23 models listed

ZEPHYR

63%

of similar heat pumps beaten by its typical model

Well above average

23 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°FIWAE: Beats 26%ZEPHYR: Beats 57%
  • Heating power kept at 5°FCapacity at 5°F vs 47°FIWAE: Beats 61%ZEPHYR: Beats 64%
  • Winter-long heating efficiencyHSPF2IWAE: Beats 35%ZEPHYR: Beats 59%
  • Summer-long cooling efficiencySEER2IWAE: Beats 40%ZEPHYR: Beats 67%
  • Hot-day cooling efficiencyEER2IWAE: Beats 36%ZEPHYR: Beats 65%

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

    IWAE
    35%
    ZEPHYR
    100%

  • Xcel CC

    IWAE
    35%
    ZEPHYR
    83%

  • CEE Advanced

    IWAE
    0%
    ZEPHYR
    9%

  • ENERGY STAR CC

    IWAE
    26%
    ZEPHYR
    74%

Top cold-climate picks, ducted 2.5–3 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 Ducted, 2.5–3 tons (27,000–38,999 Btu/h cooling). What size is my system?

IWAE

  1. 1**AESHV9T3621BAwith ducted air handler **AEAMPVT36D21BAIWAE3 tons · 34,000 Btu/h · DuctedKeeps 76% of its heat at 5°FMeets CEE 2025, CEE 2026, Xcel CC
    Heat kept at 5°F
    76% (Capacity at 5°F vs 47°F)
    Good
    Efficiency at 5°F
    1.90 (COP at 5°F)
    Below the middle
    Seasonal efficiency
    9.0 (HSPF2)
    Good
    55.4score / 100

ZEPHYR

  1. 1ZE-636HPAwith ducted air handler AH-636AZEPHYR2.5 tons · 32,000 Btu/h · DuctedKeeps 97% of its heat at 5°FMeets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    97% (Capacity at 5°F vs 47°F)
    Great
    Efficiency at 5°F
    2.15 (COP at 5°F)
    Great
    Seasonal efficiency
    10.5 (HSPF2)
    Top 10%
    87.9score / 100
  2. 2ZE-527M325ZEPHYR2.5 tons · 27,000 Btu/h · DuctedKeeps 98% of its heat at 5°FMeets CEE 2025, CEE 2026, Xcel CC, ENERGY STAR CC
    Heat kept at 5°F
    98% (Capacity at 5°F vs 47°F)
    Great
    Efficiency at 5°F
    1.80 (COP at 5°F)
    Below the middle
    Seasonal efficiency
    8.8 (HSPF2)
    Good
    56.7score / 100
  3. 3ZE-536M425ZEPHYR3 tons · 36,000 Btu/h · DuctedKeeps 90% of its heat at 5°FMeets 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
    1.80 (COP at 5°F)
    Below the middle
    Seasonal efficiency
    9.0 (HSPF2)
    Good
    54.3score / 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