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

      Panasonic CU - 4YM27CBUC

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

      Ranks #121 of 430 24,000 BTU mini-splits for cooling efficiency, and costs about $691 a year to run in a mixed climate like Atlanta.

      SEER2
      23.0 Cooling efficiency over a season
      Average · beats 62%
      HSPF2
      9.5 Heating efficiency over a season
      Below average · beats 24%
      EER2
      12.2 Cooling efficiency on a 95°F day
      Below average · beats 33%
      Heat at 5°F
      19,000 BTU/h70% of its 47°F output
      Average · beats 48%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 19,000 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.

      Calculate my running cost

      Details

      Specifications24,000 BTU, R-454B
      General
      BrandPanasonic
      Also sold asZERO, AI AIR CONDITIONING, ComfortStar, TRUST AIR CONDITIONERS, Mitsutomo, SLIMAIR, Elios, DuraSTAR, Wells, Star Air Kontrol, KEEN Home, NG Trade, Bluefin, DUCTLESSAIRE
      Outdoor unit modelCU - 4YM27CBUC
      SeriesCU Series
      TypeMini-split heat pump
      Nominal size24,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-454B
      Connected (smart) capableNo
      On the market sinceDecember 10, 2025
      Last certifiedMay 6, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better23.0 (range 21.0-23.0)
      EER2Efficiency at 95°F outdoors12.0-12.2
      Cooling capacity26,000-26,600 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.0-9.5
      Capacity at 47°F26,600-27,000 BTU/h
      Capacity at 17°F19,800-23,600 BTU/h
      Capacity at 5°F18,800-19,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.00
      ENERGY STAR cold climateYes
      Heating output as it gets colder70% 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.
      - · cold climate23.012.29.519,000218214181
      - · cold climate22.012.19.318,900218214183
      - · cold climate21.012.09.018,800218214182
      Same unit, other model numbers16

      These model numbers have exactly the same certified ratings and matchups as the Panasonic CU - 4YM27CBUC: the same equipment under another brand, or a variant code for voltage, colour or market. Everything on this page applies to them.

      Yearly running cost in 10 large cities$540-$1,715

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

      Questions5
      What is the SEER2 rating of the Panasonic CU - 4YM27CBUC?
      The Panasonic CU - 4YM27CBUC is rated at up to 23.0 SEER2 and 12.2 EER2 for cooling and up to 9.5 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 21.0-23.0.
      Is the Panasonic CU - 4YM27CBUC good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 19,000 BTU/h at 5°F with a COP of 2.00, so it is still 2.0 times as efficient as electric resistance heat at that temperature.
      How much does the Panasonic CU - 4YM27CBUC cost to run per year?
      At its rated efficiency it costs about $540-$1,715 a year in electricity in large U.S. cities, depending on climate and local rates - for example $703 in Phoenix and $1,462 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Is the Panasonic CU - 4YM27CBUC the same as the ZERO Z4SOV-27HDMB-US?
      Yes, as far as the certified ratings go. ENERGY STAR lists 17 model numbers with identical efficiency, capacity and matchups, which means the same outdoor unit sold under a different brand or with a minor variant code (voltage, colour or region). The full list is on this page.
      What refrigerant does the Panasonic CU - 4YM27CBUC use?
      It uses R-454B.

      Running cost and savings

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

      Heat pump $717/yrYou save $644/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 Panasonic CU - 4YM27CBUC
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $717
      Current system, per year
      $1,361
      You save per year
      $644
      Payback
      15.5 years
      Net after 10 years
      -$3,562

      Cooling $401Heating $316Electricity used: 4,481 kWhSaved vs. a minimum-efficiency heat pump: $328

      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 May 6, 2026. How we use the data.