HVAC Rated
    Menu

      18,000 BTU mini-split heat pump · M-Series

      Mitsubishi Electric MUZ-FS18NAH

      Below average cooling efficiency and average heating efficiency for a 18,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #319 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $466 a year to run in a mixed climate like Atlanta.

      SEER2
      21.0 Cooling efficiency over a season
      Below average · beats 30%
      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
      22,400 BTU/h118% 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 22,400 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.
      • You want the newest refrigerant - it uses R-410A, which is being phased down.

      Calculate my running cost

      Details

      Specifications18,000 BTU, R-410A
      General
      BrandMitsubishi Electric
      Also sold asAmerican Standard / Mitsubishi Electric, Trane / Mitsubishi Electric
      Outdoor unit modelMUZ-FS18NAH
      SeriesM-Series
      TypeMini-split heat pump
      Nominal size18,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-410A
      Connected (smart) capableNo
      On the market sinceDecember 1, 2022
      Last certifiedMarch 13, 2025
      Cooling
      SEER2Seasonal efficiency, higher is better21.0 (range 21.0)
      EER2Efficiency at 95°F outdoors12.5
      Cooling capacity17,200 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better10.3
      Capacity at 47°F19,000 BTU/h
      Capacity at 17°F12,800 BTU/h
      Capacity at 5°F22,400 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.00
      ENERGY STAR cold climateYes
      Heating output as it gets colder118% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with MSZ-FS18NA 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.
      MSZ-FS18NA · cold climate21.012.510.322,400209832208
      NAXWPH18B112A American Standard / Mitsubishi Electric · cold climate21.012.510.322,400213879424
      NTXWPH18B112A Trane / Mitsubishi Electric · cold climate21.012.510.322,400213879429
      Same unit, other model numbers1

      These model numbers have exactly the same certified ratings and matchups as the Mitsubishi Electric MUZ-FS18NAH: 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$387-$1,139

      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-FS18NAH?
      The Mitsubishi Electric MUZ-FS18NAH is rated at up to 21.0 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 Mitsubishi Electric MUZ-FS18NAH good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 22,400 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 Mitsubishi Electric MUZ-FS18NAH cost to run per year?
      At its rated efficiency it costs about $387-$1,139 a year in electricity in large U.S. cities, depending on climate and local rates - for example $491 in Phoenix and $963 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-FS18NAH the same as the Trane / Mitsubishi Electric NTXSPB18B112A?
      Yes, as far as the certified ratings go. ENERGY STAR lists both 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-FS18NAH?
      ENERGY STAR lists 3 certified combinations for this outdoor unit. The highest-rated ones use MSZ-FS18NA, American Standard / Mitsubishi Electric NAXWPH18B112A, Trane / Mitsubishi Electric NTXWPH18B112A.
      What refrigerant does the Mitsubishi Electric MUZ-FS18NAH 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 $495/yrYou save $421/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-FS18NAH
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $495
      Current system, per year
      $916
      You save per year
      $421
      Payback
      15.4 years
      Net after 10 years
      -$2,286

      Cooling $288Heating $207Electricity used: 3,093 kWhSaved vs. a minimum-efficiency heat pump: $212

      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 18,000 BTU models

      See all 465 18,000 BTU mini-splits, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of March 13, 2025. How we use the data.