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

      Mitsubishi Electric MUZ-HX12NL

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

      Ranks #357 of 394 12,000 BTU mini-splits for cooling efficiency, and costs about $320 a year to run in a mixed climate like Atlanta.

      SEER2
      20.0 Cooling efficiency over a season
      Below average · beats 18%
      HSPF2
      10.0 Heating efficiency over a season
      Average · beats 43%
      EER2
      12.5 Cooling efficiency on a 95°F day
      Average · beats 44%
      Heat at 5°F
      8,600 BTU/h70% 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 8,600 BTU/h at 5°F.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • Cooling cost matters most - its SEER2 is below average for mini-splits.

      Calculate my running cost

      Details

      Specifications12,000 BTU, R-454B
      General
      BrandMitsubishi Electric
      Outdoor unit modelMUZ-HX12NL
      SeriesM-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 sinceJanuary 1, 2025
      Last certifiedJanuary 14, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better20.0 (range 20.0)
      EER2Efficiency at 95°F outdoors12.5
      Cooling capacity12,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better10.0
      Capacity at 47°F12,200 BTU/h
      Capacity at 17°F7,800 BTU/h
      Capacity at 5°F8,600 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80
      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 matchup with MSZ-HX12NL 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.
      MSZ-HX12NL · cold climate20.012.510.08,600216626291
      Same unit, other model numbers3

      These model numbers have exactly the same certified ratings and matchups as the Mitsubishi Electric MUZ-HX12NL: 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$282-$767

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

      Questions6
      What is the SEER2 rating of the Mitsubishi Electric MUZ-HX12NL?
      The Mitsubishi Electric MUZ-HX12NL is rated at up to 20.0 SEER2 and 12.5 EER2 for cooling and up to 10.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the Mitsubishi Electric MUZ-HX12NL good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 8,600 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 Mitsubishi Electric MUZ-HX12NL cost to run per year?
      At its rated efficiency it costs about $282-$767 a year in electricity in large U.S. cities, depending on climate and local rates - for example $350 in Phoenix and $643 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Is the Mitsubishi Electric MUZ-HX12NL the same as the Mitsubishi Electric MUZ-JX12WL?
      Yes, as far as the certified ratings go. ENERGY STAR lists 4 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 Mitsubishi Electric MUZ-HX12NL?
      ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses MSZ-HX12NL.
      What refrigerant does the Mitsubishi Electric MUZ-HX12NL 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 $348/yrYou save $274/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 Mitsubishi Electric MUZ-HX12NL
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $348
      Current system, per year
      $622
      You save per year
      $274
      Payback
      16.4 years
      Net after 10 years
      -$1,758

      Cooling $211Heating $137Electricity used: 2,174 kWhSaved vs. a minimum-efficiency heat pump: $130

      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 January 14, 2026. How we use the data.