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

      Mitsubishi Electric MUZ-FX18NLHZ

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

      Ranks #22 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $386 a year to run in a mixed climate like Atlanta.

      SEER2
      25.5 Cooling efficiency over a season
      Very good · beats 88%
      HSPF2
      11.1 Heating efficiency over a season
      Very good · beats 78%
      EER2
      13.1 Cooling efficiency on a 95°F day
      Average · beats 68%
      Heat at 5°F
      23,600 BTU/h139% of its 47°F output
      Average · beats 61%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 88% of mini-splits.
      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 23,600 BTU/h at 5°F.
      • It will heat most of the year - its HSPF2 beats 78% of mini-splits.
      • 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

      Specifications18,000 BTU, R-454B
      General
      BrandMitsubishi Electric
      Outdoor unit modelMUZ-FX18NLHZ
      SeriesM-Series
      TypeMini-split heat pump
      Nominal size18,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-454B
      Connected (smart) capableNo
      On the market sinceJanuary 1, 2025
      Last certifiedSeptember 1, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better25.5 (range 25.5)
      EER2Efficiency at 95°F outdoors13.1
      Cooling capacity17,200 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better11.1
      Capacity at 47°F17,000 BTU/h
      Capacity at 17°F12,700 BTU/h
      Capacity at 5°F23,600 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.06
      ENERGY STAR cold climateYes
      Heating output as it gets colder139% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with MSZ-FX18NL 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-FX18NL · cold climate25.513.111.123,600215611128
      Same unit, other model numbers1

      These model numbers have exactly the same certified ratings and matchups as the Mitsubishi Electric MUZ-FX18NLHZ: 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$318-$944

      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-FX18NLHZ?
      The Mitsubishi Electric MUZ-FX18NLHZ is rated at up to 25.5 SEER2 and 13.1 EER2 for cooling and up to 11.1 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the Mitsubishi Electric MUZ-FX18NLHZ good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 23,600 BTU/h at 5°F with a COP of 2.06, so it is still 2.1 times as efficient as electric resistance heat at that temperature.
      How much does the Mitsubishi Electric MUZ-FX18NLHZ cost to run per year?
      At its rated efficiency it costs about $318-$944 a year in electricity in large U.S. cities, depending on climate and local rates - for example $405 in Phoenix and $799 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-FX18NLHZ the same as the Mitsubishi Electric MUZ-FX18NLHZ2?
      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-FX18NLHZ?
      ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses MSZ-FX18NL.
      What refrigerant does the Mitsubishi Electric MUZ-FX18NLHZ 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 $409/yrYou save $475/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-FX18NLHZ
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $409
      Current system, per year
      $884
      You save per year
      $475
      Payback
      13.7 years
      Net after 10 years
      -$1,754

      Cooling $237Heating $172Electricity used: 2,556 kWhSaved vs. a minimum-efficiency heat pump: $268

      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 September 1, 2026. How we use the data.