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      4-ton central heat pump · ML Series

      Mainline ML60HP230LMNTH-O

      Average cooling efficiency and very good heating efficiency for a 4-ton central heat pump, and certified for cold climates.

      Ranks #141 of 319 4 ton central heat pumps for cooling efficiency, and costs about $1,559 a year to run in a mixed climate like Atlanta.

      SEER2
      17.5 Cooling efficiency over a season
      Average · beats 58%
      HSPF2
      9.5 Heating efficiency over a season
      Very good · beats 70%
      EER2
      12.0 Cooling efficiency on a 95°F day
      Average · beats 64%
      Heat at 5°F
      54,000 BTU/h98% of its 47°F output
      Below average · beats 20%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 54,000 BTU/h at 5°F.
      • It will heat most of the year - its HSPF2 beats 70% of central heat pumps.
      • You want steady temperatures and quiet running - the compressor varies its speed.
      • You want a choice of indoor units - 10 certified pairings.

      Think twice if…

      • Nothing stands out - its ratings have no weak spot for its class.

      Calculate my running cost

      Details

      Specifications4 ton, R-454B
      General
      BrandMainline
      Outdoor unit modelML60HP230LMNTH-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 20, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better17.5 (range 15.2-17.5)
      EER2Efficiency at 95°F outdoors10.0-12.0
      Cooling capacity47,000-54,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better8.1-9.5
      Capacity at 47°F55,000-58,000 BTU/h
      Capacity at 17°F36,000-45,000 BTU/h
      Capacity at 5°F43,000-54,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80-1.90
      ENERGY STAR cold climateYes
      Heating output as it gets colder98% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML60HP230G3AHU-I at the standard test temperatures, in BTU/h:

      Certified matchups10 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.
      ML60HP230G3AHU-I · cold climate17.512.09.554,000217607188
      ML60HP230G3AHU-I · cold climate17.512.09.554,000216623404
      ML60HP230LMNTAHU-I · cold climate16.010.09.052,000217607181
      ML60HP230LMNTAHU-I · cold climate16.010.09.052,000215864318
      ML60HP230CC21-I · cold climate16.010.08.545,000217607217
      ML60HP230CC21-I · cold climate16.010.08.545,000216623436
      ML60HP230UC21-I · cold climate16.010.08.545,000217890350
      ML60HP230CC24-I · cold climate15.210.08.143,000217607218
      ML60HP230CC24-I · cold climate15.210.08.143,000216623437
      ML60HP230UC24-I · cold climate15.210.08.143,000217890351
      Yearly running cost in 10 large cities$1,396-$3,725

      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 ML60HP230LMNTH-O?
      The Mainline ML60HP230LMNTH-O is rated at up to 17.5 SEER2 and 12.0 EER2 for cooling and up to 9.5 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 10 certified matchups SEER2 ranges from 15.2-17.5.
      Is the Mainline ML60HP230LMNTH-O good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 54,000 BTU/h at 5°F with a COP of 1.90, so it is still 1.9 times as efficient as electric resistance heat at that temperature.
      How much does the Mainline ML60HP230LMNTH-O cost to run per year?
      At its rated efficiency it costs about $1,396-$3,725 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,720 in Phoenix and $3,112 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 ML60HP230LMNTH-O?
      ENERGY STAR lists 10 certified combinations for this outdoor unit. The highest-rated ones use ML60HP230G3AHU-I, ML60HP230LMNTAHU-I, ML60HP230CC21-I.
      What refrigerant does the Mainline ML60HP230LMNTH-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 $1,706/yrYou save $1,041/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 ML60HP230LMNTH-O
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $1,706
      Current system, per year
      $2,747
      You save per year
      $1,041
      Payback
      18.7 years
      Net after 10 years
      -$9,095

      Cooling $1,046Heating $660Electricity used: 10,663 kWhSaved vs. a minimum-efficiency heat pump: $410

      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 20, 2026. How we use the data.