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      12,000 BTU mini-split heat pump · ZMSB Series

      ZERO ZMSB-12HV-USHHCR2-O

      Very good cooling efficiency and average heating efficiency for a 12,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #179 of 394 12,000 BTU mini-splits for cooling efficiency, and costs about $287 a year to run in a mixed climate like Atlanta.

      SEER2
      24.0 Cooling efficiency over a season
      Very good · beats 75%
      HSPF2
      10.5 Heating efficiency over a season
      Average · beats 61%
      EER2
      13.2 Cooling efficiency on a 95°F day
      Average · beats 69%
      Heat at 5°F
      11,500 BTU/h96% of its 47°F output
      Below average · beats 9%

      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 11,500 BTU/h at 5°F.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • Nothing stands out - its ratings have no weak spot for its class.

      Calculate my running cost

      Details

      Specifications12,000 BTU, R-454B
      General
      BrandZERO
      Also sold asElios, PerfectAire, KEEN Home, Cadet
      Outdoor unit modelZMSB-12HV-USHHCR2-O
      SeriesZMSB Series
      TypeMini-split heat pump
      Nominal size12,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-454B
      Connected (smart) capableNo
      On the market sinceNovember 11, 2024
      Last certifiedMay 6, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better24.0 (range 24.0)
      EER2Efficiency at 95°F outdoors13.2
      Cooling capacity12,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better10.5
      Capacity at 47°F12,000 BTU/h
      Capacity at 17°F12,000 BTU/h
      Capacity at 5°F11,500 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80
      ENERGY STAR cold climateYes
      Heating output as it gets colder96% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ZMSB-12HV-USHHCR2-I 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-12HV-USHHCR2-I · cold climate24.013.210.511,500216097674
      Same unit, other model numbers4

      These model numbers have exactly the same certified ratings and matchups as the ZERO ZMSB-12HV-USHHCR2-O: 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$236-$704

      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-12HV-USHHCR2-O?
      The ZERO ZMSB-12HV-USHHCR2-O is rated at up to 24.0 SEER2 and 13.2 EER2 for cooling and up to 10.5 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the ZERO ZMSB-12HV-USHHCR2-O good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 11,500 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-12HV-USHHCR2-O cost to run per year?
      At its rated efficiency it costs about $236-$704 a year in electricity in large U.S. cities, depending on climate and local rates - for example $301 in Phoenix and $596 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Is the ZERO ZMSB-12HV-USHHCR2-O the same as the Elios ESHMA12C2AN1?
      Yes, as far as the certified ratings go. ENERGY STAR lists 5 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-12HV-USHHCR2-O?
      ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses ZMSB-12HV-USHHCR2-I.
      What refrigerant does the ZERO ZMSB-12HV-USHHCR2-O 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 $304/yrYou save $315/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-12HV-USHHCR2-O
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $304
      Current system, per year
      $619
      You save per year
      $315
      Payback
      14.3 years
      Net after 10 years
      -$1,353

      Cooling $176Heating $128Electricity used: 1,900 kWhSaved vs. a minimum-efficiency heat pump: $171

      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 12,000 BTU models

      See all 394 12,000 BTU mini-splits, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of May 6, 2026. How we use the data.