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      3-ton central heat pump · ML Series

      Mainline ML36HP230LMNTH-O

      Average cooling efficiency and excellent heating efficiency for a 3-ton central heat pump, and certified for cold climates.

      Ranks #91 of 302 3 ton central heat pumps for cooling efficiency, and costs about $987 a year to run in a mixed climate like Atlanta.

      SEER2
      18.0 Cooling efficiency over a season
      Average · beats 66%
      HSPF2
      10.3 Heating efficiency over a season
      Excellent · beats 92%
      EER2
      12.0 Cooling efficiency on a 95°F day
      Average · beats 64%
      Heat at 5°F
      39,000 BTU/h101% 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 39,000 BTU/h at 5°F.
      • It will heat most of the year - its HSPF2 beats 92% of central heat pumps.
      • You want steady temperatures and quiet running - the compressor varies its speed.
      • You want a choice of indoor units - 22 certified pairings.

      Think twice if…

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

      Calculate my running cost

      Details

      Specifications3 ton, R-454B
      General
      BrandMainline
      Outdoor unit modelML36HP230LMNTH-O
      SeriesML Series
      TypeCentral heat pump
      Nominal size3 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 better18.0 (range 15.2-18.0)
      EER2Efficiency at 95°F outdoors10.2-12.0
      Cooling capacity36,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better8.9-10.3
      Capacity at 47°F37,000-38,000 BTU/h
      Capacity at 17°F28,000-33,000 BTU/h
      Capacity at 5°F33,000-39,000 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 colder101% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML36HP230G3AHU-I at the standard test temperatures, in BTU/h:

      Certified matchups22 indoor units

      The same outdoor unit scores differently with each indoor unit and furnace. Ask your installer for the AHRI reference number of the exact system you are quoted.

      Indoor unitFurnaceSEER2EER2HSPF2Heat @5°FAHRI ref.
      ML36HP230G3AHU-I · cold climate-18.012.010.037,400217607186
      ML36HP230G3AHU-I · cold climate-18.012.010.037,400216623402
      ML36HP230LMNTAHU-I · cold climate-17.411.710.339,000217607177
      ML36HP230LMNTAHU-I · cold climate-17.411.710.339,000215864314
      ML36HP230WMAHU-I · cold climate-16.811.29.634,600217607199
      ML36HP230WMAHU-I · cold climate-16.811.29.634,600216623415
      ML36HP230CC17-I · cold climate-15.810.79.436,000217607214
      ML36HP230CC21-I · cold climate-15.810.79.436,000217607216
      ML36HP230CC21-I · cold climate-15.810.79.436,000216623435
      ML36HP230CC17-I · cold climate-15.810.79.436,000216623433
      ML36HP230UC17-I · cold climate-15.810.79.436,000217890345
      ML36HP230UC21-I · cold climate-15.810.79.436,000217890347
      ML36HP230CC17-I · cold climateS9V2B080U4VS***15.510.49.233,000217607238
      ML36HP230CC17-I · cold climateS9V2B080U4VS***15.510.49.233,000217550377
      ML36HP230PCAHU-I · cold climate-15.410.29.836,000217607205
      ML36HP230PCAHU-I · cold climate-15.410.29.836,000216623422
      ML36HP230CC17-I · cold climateS9V2B040U3VS***15.310.38.933,000217607235
      ML36HP230CC17-I · cold climateS9V2B040U3VS***15.310.38.933,000217550374
      ML36HP230CC17-I · cold climateS9V2B060U4VS***15.210.39.033,000217607236
      ML36HP230CC17-I · cold climateS9V2B060D3VS***15.210.39.033,000217607237
      ML36HP230CC17-I · cold climateS9V2B060U4VS***15.210.39.033,000217550375
      ML36HP230CC17-I · cold climateS9V2B060D3VS***15.210.39.033,000217550376
      Yearly running cost in 10 large cities$937-$2,316

      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 ML36HP230LMNTH-O?
      The Mainline ML36HP230LMNTH-O is rated at up to 18.0 SEER2 and 12.0 EER2 for cooling and up to 10.3 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 22 certified matchups SEER2 ranges from 15.2-18.0.
      Is the Mainline ML36HP230LMNTH-O good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 39,000 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 ML36HP230LMNTH-O cost to run per year?
      At its rated efficiency it costs about $937-$2,316 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,129 in Phoenix and $1,915 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 ML36HP230LMNTH-O?
      ENERGY STAR lists 22 certified combinations for this outdoor unit. The highest-rated ones use ML36HP230G3AHU-I, ML36HP230LMNTAHU-I, ML36HP230WMAHU-I.
      What refrigerant does the Mainline ML36HP230LMNTH-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 $1,106/yrYou save $766/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 ML36HP230LMNTH-O
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $1,106
      Current system, per year
      $1,873
      You save per year
      $766
      Payback
      17.6 years
      Net after 10 years
      -$5,837

      Cooling $704Heating $402Electricity used: 6,915 kWhSaved vs. a minimum-efficiency heat pump: $332

      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 3 ton models

      See all 302 3 ton central heat pumps, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of August 20, 2026. How we use the data.