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      18,000 BTU mini-split heat pump · 45M Series

      Carrier 37MPRAQ18AA3

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

      Ranks #17 of 465 18,000 BTU mini-splits for cooling efficiency.

      SEER2
      25.8 Cooling efficiency over a season
      Excellent · beats 90%
      HSPF2
      - Heating efficiency over a season
      EER2
      15.0 Cooling efficiency on a 95°F day
      Excellent · beats 91%
      Heat at 5°F
      22,600 BTU/h113% of its 47°F output
      Very good · beats 89%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 90% of mini-splits.
      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 22,600 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

      Specifications18,000 BTU, R-454B
      General
      BrandCarrier
      Also sold asBryant, Payne, WeatherMaker, Midea
      Outdoor unit model37MPRAQ18AA3
      Series45M 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 sinceNovember 15, 2018
      Last certifiedApril 21, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better25.8 (range 25.8)
      EER2Efficiency at 95°F outdoors15.0
      Cooling capacity18,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better-
      Capacity at 47°F20,000 BTU/h
      Capacity at 17°F19,300 BTU/h
      Capacity at 5°F22,600 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.34
      ENERGY STAR cold climateYes
      Heating output as it gets colder113% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with 45MPHAQ18XA3 at the standard test temperatures, in BTU/h:

      Certified matchups7 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.
      45MPHAQ18XA3 CARRIER · cold climate25.815.0-22,600215413144
      615PHAQ18XA3 BRYANT · cold climate25.815.0-22,600215413150
      D5MPHAQ18XA3 PAYNE · cold climate25.815.0-22,600215413156
      D5MPHAQ18XA3 Weathermaker · cold climate25.815.0-22,600215413162
      D5MPHAQ18XA3 MIDEA · cold climate25.815.0-22,600215413168
      D5MPHAQ18XA3 BRYANT · cold climate25.815.0-22,600218139618
      D5MPHAQ18XA3 CARRIER · cold climate25.815.0-22,600218139614
      Questions4
      What is the SEER2 rating of the Carrier 37MPRAQ18AA3?
      The Carrier 37MPRAQ18AA3 is rated at up to 25.8 SEER2 and 15.0 EER2 for cooling and up to - HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the Carrier 37MPRAQ18AA3 good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 22,600 BTU/h at 5°F with a COP of 2.34, so it is still 2.3 times as efficient as electric resistance heat at that temperature.
      Which indoor units work with the Carrier 37MPRAQ18AA3?
      ENERGY STAR lists 7 certified combinations for this outdoor unit. The highest-rated ones use CARRIER 45MPHAQ18XA3, BRYANT 615PHAQ18XA3, PAYNE D5MPHAQ18XA3.
      What refrigerant does the Carrier 37MPRAQ18AA3 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 $494/yrYou save $466/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 Carrier 37MPRAQ18AA3
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $494
      Current system, per year
      $961
      You save per year
      $466
      Payback
      15.0 years
      Net after 10 years
      -$2,336

      Cooling $246Heating $249Electricity used: 3,090 kWhSaved vs. a minimum-efficiency heat pump: $247

      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

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      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of April 21, 2026. How we use the data.