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      9,000 BTU mini-split heat pump · SZ Series

      Sea Breeze SZ9H424ZMO

      Very good cooling and heating efficiency for a 9,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #198 of 395 9,000 BTU mini-splits for cooling efficiency, and costs about $212 a year to run in a mixed climate like Atlanta.

      SEER2
      24.0 Cooling efficiency over a season
      Very good · beats 75%
      HSPF2
      12.0 Heating efficiency over a season
      Very good · beats 89%
      EER2
      14.7 Cooling efficiency on a 95°F day
      Very good · beats 89%
      Heat at 5°F
      8,000 BTU/h75% of its 47°F output
      Very good · beats 89%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 75% of mini-splits.
      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 8,000 BTU/h at 5°F.
      • It will heat most of the year - its HSPF2 beats 89% of mini-splits.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • You want the newest refrigerant - it uses R-410A, which is being phased down.

      Calculate my running cost

      Details

      Specifications9,000 BTU, R-410A
      General
      BrandSea Breeze
      Outdoor unit modelSZ9H424ZMO
      SeriesSZ Series
      TypeMini-split heat pump
      Nominal size9,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-410A
      Connected (smart) capableNo
      On the market sinceFebruary 28, 2025
      Last certifiedApril 17, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better24.0 (range 19.2-24.0)
      EER2Efficiency at 95°F outdoors12.5-15.0
      Cooling capacity6,000-9,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better10.0-12.0
      Capacity at 47°F7,000-11,000 BTU/h
      Capacity at 17°F7,500-8,100 BTU/h
      Capacity at 5°F7,100-8,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.84-2.34
      ENERGY STAR cold climateYes
      Heating output as it gets colder75% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with WM9H424ZMI at the standard test temperatures, in BTU/h:

      Certified matchups5 indoor units

      The same outdoor unit scores differently with each indoor unit. Ask your installer for the AHRI reference number of the exact system you are quoted.

      Indoor unitSEER2EER2HSPF2Heat @5°FAHRI ref.
      WM9H424ZMI SEA BREEZE+ · cold climate24.014.711.67,500208674954
      WM6H424ZMI SEA BREEZE+ · cold climate23.515.012.07,100208128266
      SCA9H424ZMI SEA BREEZE+ · cold climate22.513.011.57,700210404149
      CA9H424ZMI SEA BREEZE+ · cold climate20.013.010.07,400208128270
      D9H424ZMI SEA BREEZE+ · cold climate19.212.510.28,000208128276
      Yearly running cost in 10 large cities$177-$516

      At each state's average electricity price and the city's typical heating and cooling hours.

      Questions5
      What is the SEER2 rating of the Sea Breeze SZ9H424ZMO?
      The Sea Breeze SZ9H424ZMO is rated at up to 24.0 SEER2 and 14.7 EER2 for cooling and up to 12.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 5 certified matchups SEER2 ranges from 19.2-24.0.
      Is the Sea Breeze SZ9H424ZMO good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 8,000 BTU/h at 5°F with a COP of 2.34, so it is still 2.3 times as efficient as electric resistance heat at that temperature.
      How much does the Sea Breeze SZ9H424ZMO cost to run per year?
      At its rated efficiency it costs about $177-$516 a year in electricity in large U.S. cities, depending on climate and local rates - for example $224 in Phoenix and $436 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Which indoor units work with the Sea Breeze SZ9H424ZMO?
      ENERGY STAR lists 5 certified combinations for this outdoor unit. The highest-rated ones use SEA BREEZE+ WM9H424ZMI, SEA BREEZE+ WM6H424ZMI, SEA BREEZE+ SCA9H424ZMI.
      What refrigerant does the Sea Breeze SZ9H424ZMO use?
      It uses R-410A. R-410A is being phased down under the EPA AIM Act, and new systems are moving to R-454B and R-32.

      Running cost and savings

      Pre-filled with this model. Pick your city and what you heat with today; everything else is optional.

      Heat pump $225/yrYou save $255/yrSee details ↓
      1. Where you live
      Adjust heating and cooling hours

      Filled in from your city's climate. Change them if you run the system much more or less than usual.

      2. The heat pump Sea Breeze SZ9H424ZMO
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $225
      Current system, per year
      $480
      You save per year
      $255
      Payback
      13.7 years
      Net after 10 years
      -$949

      Cooling $132Heating $93Electricity used: 1,408 kWhSaved vs. a minimum-efficiency heat pump: $146

      Estimates use the unit's rated SEER2 and HSPF2, full-load hours derived from NOAA 1991-2020 degree days, average residential electricity prices from the U.S. EIA (12 months to July 2026) and fuel prices from EIA (2025 for natural gas, week of 2026-10-05 for propane and heating oil). Very cold days that need backup heat are not modelled. Federal minimum for comparison: 14.3 SEER2 / 7.5 HSPF2.

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      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of April 17, 2026. How we use the data.