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      48,000 BTU mini-split heat pump · ML Series

      Mainline ML48HP230LCM-O

      Below average cooling efficiency and average heating efficiency for a 48,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #89 of 146 48,000 BTU mini-splits for cooling efficiency, and costs about $1,288 a year to run in a mixed climate like Atlanta.

      SEER2
      19.8 Cooling efficiency over a season
      Below average · beats 14%
      HSPF2
      10.2 Heating efficiency over a season
      Average · beats 53%
      EER2
      9.5 Cooling efficiency on a 95°F day
      Below average · beats 3%
      Heat at 5°F
      40,500 BTU/h77% of its 47°F output
      Very good · beats 71%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 40,500 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.

      Calculate my running cost

      Details

      Specifications48,000 BTU, R-454B
      General
      BrandMainline
      Outdoor unit modelML48HP230LCM-O
      SeriesML Series
      TypeMini-split heat pump
      Nominal size48,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-454B
      Connected (smart) capableNo
      On the market sinceMay 20, 2024
      Last certifiedAugust 19, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better19.8 (range 17.1-19.8)
      EER2Efficiency at 95°F outdoors9.5-10.0
      Cooling capacity48,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.8-10.2
      Capacity at 47°F50,000 BTU/h
      Capacity at 17°F36,600-40,000 BTU/h
      Capacity at 5°F35,200-40,500 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.90-2.11
      ENERGY STAR cold climateYes
      Heating output as it gets colder77% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML48HP230FLO-I at the standard test temperatures, in BTU/h:

      Certified matchups8 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.
      ML48HP230FLO-I MAINLINE · cold climate19.89.510.238,500217607306
      ML48HP230FLO-I MAINLINE · cold climate19.89.510.238,500215864396
      ML48HP230STDCAS-I MAINLINE · cold climate19.09.59.940,500217607304
      ML48HP230STDCAS-I MAINLINE · cold climate19.09.59.940,500215864391
      ML48HP230RS485AHU-I · cold climate17.710.010.035,200217607164
      ML48HP230RS485AHU-I · cold climate17.710.010.035,200215864299
      ML48HP230HSDUC-I MAINLINE · cold climate17.110.09.838,000217607305
      ML48HP230HSDUC-I MAINLINE · cold climate17.110.09.838,000215864393
      Yearly running cost in 10 large cities$1,140-$3,087

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

      Questions5
      What is the SEER2 rating of the Mainline ML48HP230LCM-O?
      The Mainline ML48HP230LCM-O is rated at up to 19.8 SEER2 and 9.5 EER2 for cooling and up to 10.2 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 8 certified matchups SEER2 ranges from 17.1-19.8.
      Is the Mainline ML48HP230LCM-O good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 40,500 BTU/h at 5°F with a COP of 2.11, so it is still 2.1 times as efficient as electric resistance heat at that temperature.
      How much does the Mainline ML48HP230LCM-O cost to run per year?
      At its rated efficiency it costs about $1,140-$3,087 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,411 in Phoenix and $2,583 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 Mainline ML48HP230LCM-O?
      ENERGY STAR lists 8 certified combinations for this outdoor unit. The highest-rated ones use MAINLINE ML48HP230FLO-I, MAINLINE ML48HP230STDCAS-I, ML48HP230RS485AHU-I.
      What refrigerant does the Mainline ML48HP230LCM-O 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 $1,402/yrYou save $1,105/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 Mainline ML48HP230LCM-O
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $1,402
      Current system, per year
      $2,508
      You save per year
      $1,105
      Payback
      16.3 years
      Net after 10 years
      -$6,946

      Cooling $853Heating $549Electricity used: 8,765 kWhSaved vs. a minimum-efficiency heat pump: $526

      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 August 19, 2026. How we use the data.