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      18,000 BTU mini-split heat pump · 37M Series

      Carrier 37MHRAQ18AA3

      Below average cooling and heating efficiency for a 18,000 BTU mini-split heat pump, but not rated for cold climates.

      Ranks #385 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $516 a year to run in a mixed climate like Atlanta.

      SEER2
      20.3 Cooling efficiency over a season
      Below average · beats 23%
      HSPF2
      9.1 Heating efficiency over a season
      Below average · beats 13%
      EER2
      11.5 Cooling efficiency on a 95°F day
      Below average · beats 13%
      Heat at 5°F
      11,500 BTU/h61% of its 47°F output
      Average · beats 48%

      A good fit if…

      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • You often see nights below 0°F - it is not cold-climate certified.
      • 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-454B
      General
      BrandCarrier
      Also sold asBryant, Payne, WeatherMaker, Midea
      Outdoor unit model37MHRAQ18AA3
      Series37M 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 certifiedMay 6, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better20.3 (range 20.3)
      EER2Efficiency at 95°F outdoors11.5
      Cooling capacity18,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.1
      Capacity at 47°F18,800 BTU/h
      Capacity at 17°F14,000 BTU/h
      Capacity at 5°F11,500 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.00
      ENERGY STAR cold climateNo
      Heating output as it gets colder61% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with 45MHHAQ18XC3 at the standard test temperatures, in BTU/h:

      Certified matchups5 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.
      45MHHAQ18XC3 CARRIER20.311.59.111,500215413175
      45MHHAQ18XC3 BRYANT20.311.59.111,500215413183
      45MHHAQ18XC3 PAYNE20.311.59.111,500215413191
      45MHHAQ18XC3 Weathermaker20.311.59.111,500215413199
      45MHHAQ18XC3 MIDEA20.311.59.111,500215413207
      Yearly running cost in 10 large cities$419-$1,268

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

      Questions5
      What is the SEER2 rating of the Carrier 37MHRAQ18AA3?
      The Carrier 37MHRAQ18AA3 is rated at up to 20.3 SEER2 and 11.5 EER2 for cooling and up to 9.1 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the Carrier 37MHRAQ18AA3 good for cold climates?
      It is not cold-climate certified: none of its matchups meet the ENERGY STAR cold-climate criteria (a COP of at least 1.75 at 5°F among other limits). In places with frequent sub-zero nights, pick a cold-climate 18,000 BTU model.
      How much does the Carrier 37MHRAQ18AA3 cost to run per year?
      At its rated efficiency it costs about $419-$1,268 a year in electricity in large U.S. cities, depending on climate and local rates - for example $537 in Phoenix and $1,075 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 Carrier 37MHRAQ18AA3?
      ENERGY STAR lists 5 certified combinations for this outdoor unit. The highest-rated ones use CARRIER 45MHHAQ18XC3, BRYANT 45MHHAQ18XC3, PAYNE 45MHHAQ18XC3.
      What refrigerant does the Carrier 37MHRAQ18AA3 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 $544/yrYou save $398/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 37MHRAQ18AA3
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $544
      Current system, per year
      $941
      You save per year
      $398
      Payback
      17.6 years
      Net after 10 years
      -$3,023

      Cooling $312Heating $231Electricity used: 3,397 kWhSaved vs. a minimum-efficiency heat pump: $180

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

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of May 6, 2026. How we use the data.