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      18,000 BTU mini-split heat pump · AIRSTAGE H-Series

      Fujitsu AOUH18KNAS1

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

      Ranks #416 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $508 a year to run in a mixed climate like Atlanta.

      SEER2
      20.0 Cooling efficiency over a season
      Below average · beats 18%
      HSPF2
      9.0 Heating efficiency over a season
      Below average · beats 10%
      EER2
      11.0 Cooling efficiency on a 95°F day
      Below average · beats 9%
      Heat at 5°F
      14,500 BTU/h81% of its 47°F output
      Average · beats 59%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 14,500 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 mainly need heat - its HSPF2 is below average for mini-splits.

      Calculate my running cost

      Details

      Specifications18,000 BTU, R-32
      General
      BrandFujitsu
      Outdoor unit modelAOUH18KNAS1
      SeriesAIRSTAGE H-Series
      TypeMini-split heat pump
      Nominal size18,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-32
      Connected (smart) capableNo
      On the market sinceAugust 1, 2025
      Last certifiedApril 27, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better20.0 (range 20.0)
      EER2Efficiency at 95°F outdoors11.0
      Cooling capacity18,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.0
      Capacity at 47°F18,000 BTU/h
      Capacity at 17°F12,400 BTU/h
      Capacity at 5°F14,500 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.02
      ENERGY STAR cold climateYes
      Heating output as it gets colder81% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ASUH18KNAS 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.
      ASUH18KNAS FUJITSU · cold climate20.011.09.014,500217617837
      Yearly running cost in 10 large cities$425-$1,238

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

      Questions5
      What is the SEER2 rating of the Fujitsu AOUH18KNAS1?
      The Fujitsu AOUH18KNAS1 is rated at up to 20.0 SEER2 and 11.0 EER2 for cooling and up to 9.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the Fujitsu AOUH18KNAS1 good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 14,500 BTU/h at 5°F with a COP of 2.02, so it is still 2.0 times as efficient as electric resistance heat at that temperature.
      How much does the Fujitsu AOUH18KNAS1 cost to run per year?
      At its rated efficiency it costs about $425-$1,238 a year in electricity in large U.S. cities, depending on climate and local rates - for example $538 in Phoenix and $1,045 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Which indoor units work with the Fujitsu AOUH18KNAS1?
      ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses FUJITSU ASUH18KNAS.
      What refrigerant does the Fujitsu AOUH18KNAS1 use?
      It uses 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 $541/yrYou save $387/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 Fujitsu AOUH18KNAS1
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $541
      Current system, per year
      $928
      You save per year
      $387
      Payback
      18.1 years
      Net after 10 years
      -$3,127

      Cooling $317Heating $224Electricity used: 3,380 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.

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      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of April 27, 2026. How we use the data.