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      4-ton central heat pump · ML Series

      Mainline ML50HP230LMNTH-O

      Below average cooling efficiency and average heating efficiency for a 4-ton central heat pump, and certified for cold climates.

      Ranks #201 of 319 4 ton central heat pumps for cooling efficiency, and costs about $1,608 a year to run in a mixed climate like Atlanta.

      SEER2
      16.3 Cooling efficiency over a season
      Below average · beats 37%
      HSPF2
      9.0 Heating efficiency over a season
      Average · beats 54%
      EER2
      11.7 Cooling efficiency on a 95°F day
      Average · beats 43%
      Heat at 5°F
      52,000 BTU/h93% of its 47°F output
      Below average · beats 5%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 52,000 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 central heat pumps.

      Calculate my running cost

      Details

      Specifications4 ton, R-454B
      General
      BrandMainline
      Outdoor unit modelML50HP230LMNTH-O
      SeriesML Series
      TypeCentral heat pump
      Nominal size4 ton
      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 better16.3 (range 16.3)
      EER2Efficiency at 95°F outdoors11.7
      Cooling capacity48,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.0
      Capacity at 47°F56,000 BTU/h
      Capacity at 17°F45,000 BTU/h
      Capacity at 5°F52,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80
      ENERGY STAR cold climateYes
      Heating output as it gets colder93% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML50HP230LMNTAHU-I at the standard test temperatures, in BTU/h:

      Certified matchups2 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.
      ML50HP230LMNTAHU-I · cold climate16.311.79.052,000217607180
      ML50HP230LMNTAHU-I · cold climate16.311.79.052,000215864317
      Yearly running cost in 10 large cities$1,387-$3,886

      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 ML50HP230LMNTH-O?
      The Mainline ML50HP230LMNTH-O is rated at up to 16.3 SEER2 and 11.7 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 Mainline ML50HP230LMNTH-O good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 52,000 BTU/h at 5°F with a COP of 1.80, so it is still 1.8 times as efficient as electric resistance heat at that temperature.
      How much does the Mainline ML50HP230LMNTH-O cost to run per year?
      At its rated efficiency it costs about $1,387-$3,886 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,734 in Phoenix and $3,266 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 ML50HP230LMNTH-O?
      ENERGY STAR lists 2 certified combinations for this outdoor unit. The highest-rated one uses ML50HP230LMNTAHU-I.
      What refrigerant does the Mainline ML50HP230LMNTH-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 $1,733/yrYou save $872/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 ML50HP230LMNTH-O
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $1,733
      Current system, per year
      $2,606
      You save per year
      $872
      Payback
      20.6 years
      Net after 10 years
      -$9,276

      Cooling $1,037Heating $697Electricity used: 10,834 kWhSaved vs. a minimum-efficiency heat pump: $284

      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 4 ton models

      See all 319 4 ton central heat pumps, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of August 19, 2026. How we use the data.