HVAC Rated
    Menu

      24,000 BTU mini-split heat pump · MZ Series

      Sea Breeze MZ27H424ZMO

      Average cooling efficiency and below average heating efficiency for a 24,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #170 of 430 24,000 BTU mini-splits for cooling efficiency, and costs about $621 a year to run in a mixed climate like Atlanta.

      SEER2
      22.3 Cooling efficiency over a season
      Average · beats 53%
      HSPF2
      9.7 Heating efficiency over a season
      Below average · beats 31%
      EER2
      12.5 Cooling efficiency on a 95°F day
      Average · beats 44%
      Heat at 5°F
      18,000 BTU/h71% of its 47°F output
      Below average · beats 27%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 18,000 BTU/h at 5°F.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • You mainly need heat - its HSPF2 is below average for mini-splits.
      • You want the newest refrigerant - it uses R-410A, which is being phased down.

      Calculate my running cost

      Details

      Specifications24,000 BTU, R-410A
      General
      BrandSea Breeze
      Outdoor unit modelMZ27H424ZMO
      SeriesMZ Series
      TypeMini-split heat pump
      Nominal size24,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-410A
      Connected (smart) capableNo
      On the market sinceFebruary 28, 2025
      Last certifiedJune 13, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better22.3 (range 21.3-22.3)
      EER2Efficiency at 95°F outdoors12.5
      Cooling capacity24,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.6-9.7
      Capacity at 47°F24,000 BTU/h
      Capacity at 17°F18,000-21,600 BTU/h
      Capacity at 5°F17,000-18,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.83-1.90
      ENERGY STAR cold climateYes
      Heating output as it gets colder71% kept at 5°F

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

      Certified matchups3 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.
      - SEA BREEZE+ · cold climate22.312.59.617,000208128285
      - SEA BREEZE+ · cold climate21.812.59.717,500208128287
      - SEA BREEZE+ · cold climate21.312.59.718,000208128286
      Yearly running cost in 10 large cities$508-$1,522

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

      Questions4
      What is the SEER2 rating of the Sea Breeze MZ27H424ZMO?
      The Sea Breeze MZ27H424ZMO is rated at up to 22.3 SEER2 and 12.5 EER2 for cooling and up to 9.7 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 21.3-22.3.
      Is the Sea Breeze MZ27H424ZMO good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 18,000 BTU/h at 5°F with a COP of 1.90, so it is still 1.9 times as efficient as electric resistance heat at that temperature.
      How much does the Sea Breeze MZ27H424ZMO cost to run per year?
      At its rated efficiency it costs about $508-$1,522 a year in electricity in large U.S. cities, depending on climate and local rates - for example $649 in Phoenix and $1,289 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      What refrigerant does the Sea Breeze MZ27H424ZMO 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 $656/yrYou save $582/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 MZ27H424ZMO
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $656
      Current system, per year
      $1,238
      You save per year
      $582
      Payback
      15.5 years
      Net after 10 years
      -$3,184

      Cooling $379Heating $277Electricity used: 4,100 kWhSaved vs. a minimum-efficiency heat pump: $293

      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.

      Similar 24,000 BTU models

      See all 430 24,000 BTU mini-splits, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of June 13, 2026. How we use the data.