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      18,000 BTU mini-split heat pump · BMS500

      Bosch BMS500-AAS018-1CSXRC

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

      Ranks #115 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $449 a year to run in a mixed climate like Atlanta.

      SEER2
      23.5 Cooling efficiency over a season
      Very good · beats 70%
      HSPF2
      10.8 Heating efficiency over a season
      Very good · beats 71%
      EER2
      12.5 Cooling efficiency on a 95°F day
      Average · beats 44%
      Heat at 5°F
      13,000 BTU/h59% of its 47°F output
      Excellent · beats 93%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 70% of mini-splits.
      • It will heat most of the year - its HSPF2 beats 71% of mini-splits.
      • 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.
      • 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
      BrandBosch
      Also sold asTRUST AIR CONDITIONERS
      Outdoor unit modelBMS500-AAS018-1CSXRC
      SeriesBMS500
      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 sinceJanuary 1, 2022
      Last certifiedMay 12, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better23.5 (range 20.0-23.5)
      EER2Efficiency at 95°F outdoors12.5
      Cooling capacity16,000-18,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better10.5-10.8
      Capacity at 47°F19,000-20,000 BTU/h
      Capacity at 17°F12,000-14,900 BTU/h
      Capacity at 5°F11,300-13,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.02-2.40
      ENERGY STAR cold climateNo
      Heating output as it gets colder59% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with BMS500-AAU018-1AHWXC at the standard test temperatures, in BTU/h:

      Certified matchups4 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.
      BMS500-AAU018-1AHWXC BOSCH23.512.510.811,300207759991
      BMS500-AAU018-1AHCXB BOSCH20.512.510.512,700207760015
      BMS500-AAU018-1AHDXB BOSCH20.012.510.613,000207760004
      BMS500-AAU018-1AHDXB BOSCH20.012.510.613,000207760004
      Same unit, other model numbers1

      These model numbers have exactly the same certified ratings and matchups as the Bosch BMS500-AAS018-1CSXRC: 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$343-$1,120

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

      Questions6
      What is the SEER2 rating of the Bosch BMS500-AAS018-1CSXRC?
      The Bosch BMS500-AAS018-1CSXRC is rated at up to 23.5 SEER2 and 12.5 EER2 for cooling and up to 10.8 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 4 certified matchups SEER2 ranges from 20.0-23.5.
      Is the Bosch BMS500-AAS018-1CSXRC 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 Bosch BMS500-AAS018-1CSXRC cost to run per year?
      At its rated efficiency it costs about $343-$1,120 a year in electricity in large U.S. cities, depending on climate and local rates - for example $451 in Phoenix and $957 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Is the Bosch BMS500-AAS018-1CSXRC the same as the TRUST AIR CONDITIONERS OUS18H/O4S4P?
      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 Bosch BMS500-AAS018-1CSXRC?
      ENERGY STAR lists 4 certified combinations for this outdoor unit. The highest-rated ones use BOSCH BMS500-AAU018-1AHWXC, BOSCH BMS500-AAU018-1AHCXB, BOSCH BMS500-AAU018-1AHDXB.
      What refrigerant does the Bosch BMS500-AAS018-1CSXRC 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 $462/yrYou save $464/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 Bosch BMS500-AAS018-1CSXRC
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $462
      Current system, per year
      $926
      You save per year
      $464
      Payback
      14.0 years
      Net after 10 years
      -$1,864

      Cooling $255Heating $207Electricity used: 2,888 kWhSaved vs. a minimum-efficiency heat pump: $255

      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 May 12, 2026. How we use the data.