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

      ZERO ZMSB-24HV-USHHC

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

      Ranks #169 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
      10.3 Heating efficiency over a season
      Average · beats 55%
      EER2
      12.5 Cooling efficiency on a 95°F day
      Average · beats 44%
      Heat at 5°F
      23,000 BTU/h88% of its 47°F output
      Below average · beats 9%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 23,000 BTU/h at 5°F.
      • 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

      Specifications24,000 BTU, R-410A
      General
      BrandZERO
      Also sold asAI AIR CONDITIONING, SLIMAIR, Wells, PerfectAire, ECO AC, Premium Levella, Bluefin
      Outdoor unit modelZMSB-24HV-USHHC
      SeriesZMSB 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 sinceMarch 27, 2024
      Last certifiedApril 17, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better22.3 (range 22.3)
      EER2Efficiency at 95°F outdoors12.5
      Cooling capacity23,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better10.3
      Capacity at 47°F26,000 BTU/h
      Capacity at 17°F18,900 BTU/h
      Capacity at 5°F23,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80
      ENERGY STAR cold climateYes
      Heating output as it gets colder88% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ZMSB-24HV-USHHC at the standard test temperatures, in BTU/h:

      Certified matchups1 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.
      ZMSB-24HV-USHHC · cold climate22.312.510.323,000214232450
      Same unit, other model numbers8

      These model numbers have exactly the same certified ratings and matchups as the ZERO ZMSB-24HV-USHHC: 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$488-$1,537

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

      Questions6
      What is the SEER2 rating of the ZERO ZMSB-24HV-USHHC?
      The ZERO ZMSB-24HV-USHHC is rated at up to 22.3 SEER2 and 12.5 EER2 for cooling and up to 10.3 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the ZERO ZMSB-24HV-USHHC good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 23,000 BTU/h at 5°F with a COP of 1.80, so it is still 1.8 times as efficient as electric resistance heat at that temperature.
      How much does the ZERO ZMSB-24HV-USHHC cost to run per year?
      At its rated efficiency it costs about $488-$1,537 a year in electricity in large U.S. cities, depending on climate and local rates - for example $634 in Phoenix and $1,309 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Is the ZERO ZMSB-24HV-USHHC the same as the ZERO ZMSB-24HV-USHHC-O?
      Yes, as far as the certified ratings go. ENERGY STAR lists 9 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.
      Which indoor units work with the ZERO ZMSB-24HV-USHHC?
      ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses ZMSB-24HV-USHHC.
      What refrigerant does the ZERO ZMSB-24HV-USHHC 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 $646/yrYou save $589/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 ZERO ZMSB-24HV-USHHC
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $646
      Current system, per year
      $1,235
      You save per year
      $589
      Payback
      14.4 years
      Net after 10 years
      -$2,607

      Cooling $363Heating $283Electricity used: 4,036 kWhSaved vs. a minimum-efficiency heat pump: $309

      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 April 17, 2026. How we use the data.