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      2-ton central heat pump · ML Series

      Mainline ML24HP230LMNTH-O

      Very good cooling efficiency and excellent heating efficiency for a 2-ton central heat pump, and certified for cold climates.

      Ranks #76 of 331 2 ton central heat pumps for cooling efficiency, and costs about $647 a year to run in a mixed climate like Atlanta.

      SEER2
      18.6 Cooling efficiency over a season
      Very good · beats 79%
      HSPF2
      10.5 Heating efficiency over a season
      Excellent · beats 96%
      EER2
      12.0 Cooling efficiency on a 95°F day
      Average · beats 64%
      Heat at 5°F
      21,600 BTU/h86% of its 47°F output
      Average · beats 67%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 79% of central heat pumps.
      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 21,600 BTU/h at 5°F.
      • It will heat most of the year - its HSPF2 beats 96% of central heat pumps.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

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

      Calculate my running cost

      Details

      Specifications2 ton, R-454B
      General
      BrandMainline
      Outdoor unit modelML24HP230LMNTH-O
      SeriesML Series
      TypeCentral heat pump
      Nominal size2 ton
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-454B
      Connected (smart) capableNo
      On the market sinceMay 20, 2024
      Last certifiedSeptember 30, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better18.6 (range 16.0-18.6)
      EER2Efficiency at 95°F outdoors10.0-12.0
      Cooling capacity23,000-24,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better8.5-10.5
      Capacity at 47°F24,000-26,000 BTU/h
      Capacity at 17°F18,000-20,800 BTU/h
      Capacity at 5°F19,600-21,600 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80-2.14
      ENERGY STAR cold climateYes
      Heating output as it gets colder86% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML24HP230G3AHU-I at the standard test temperatures, in BTU/h:

      Certified matchups20 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.
      ML24HP230G3AHU-I · cold climate-18.612.010.020,600217607183
      ML24HP230G3AHU-I · cold climate-18.612.010.020,600216623399
      ML24HP230LMNTAHU-I · cold climate-18.311.710.021,600217607174
      ML24HP230LMNTAHU-I · cold climate-18.311.710.021,600215864311
      ML24HP230WMAHU-I · cold climate-17.510.810.519,600217607197
      ML24HP230WMAHU-I · cold climate-17.510.810.519,600216623413
      ML24HP230PCAHU-I · cold climate-17.510.89.220,000217607203
      ML24HP230PCAHU-I · cold climate-17.510.89.220,000216623420
      ML24HP230CC17-I · cold climateS9V2B040U3VS***17.210.58.520,000217607232
      ML24HP230CC17-I · cold climateS9V2B060U4VS***17.210.58.520,000217607233
      ML24HP230CC17-I · cold climateS9V2B060D3VS***17.210.58.520,000217607234
      ML24HP230CC17-I · cold climateS9V2B040U3VS***17.210.58.520,000217550371
      ML24HP230CC17-I · cold climateS9V2B060U4VS***17.210.58.520,000217550372
      ML24HP230CC17-I · cold climateS9V2B060D3VS***17.210.58.520,000217550373
      ML24HP230CC14-I · cold climate-16.010.09.521,000217607209
      ML24HP230CC17-I · cold climate-16.010.09.521,000217607211
      ML24HP230CC17-I · cold climate-16.010.09.521,000216623430
      ML24HP230CC14-I · cold climate-16.010.09.521,000216623428
      ML24HP230UC14-I · cold climate-16.010.09.521,000217902708
      ML24HP230UC17-I · cold climate-16.010.09.521,000217902710
      Yearly running cost in 10 large cities$605-$1,526

      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 ML24HP230LMNTH-O?
      The Mainline ML24HP230LMNTH-O is rated at up to 18.6 SEER2 and 12.0 EER2 for cooling and up to 10.5 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 20 certified matchups SEER2 ranges from 16.0-18.6.
      Is the Mainline ML24HP230LMNTH-O good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 21,600 BTU/h at 5°F with a COP of 2.14, so it is still 2.1 times as efficient as electric resistance heat at that temperature.
      How much does the Mainline ML24HP230LMNTH-O cost to run per year?
      At its rated efficiency it costs about $605-$1,526 a year in electricity in large U.S. cities, depending on climate and local rates - for example $733 in Phoenix and $1,266 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 ML24HP230LMNTH-O?
      ENERGY STAR lists 20 certified combinations for this outdoor unit. The highest-rated ones use ML24HP230G3AHU-I, ML24HP230LMNTAHU-I, ML24HP230WMAHU-I.
      What refrigerant does the Mainline ML24HP230LMNTH-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 $721/yrYou save $533/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 ML24HP230LMNTH-O
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $721
      Current system, per year
      $1,254
      You save per year
      $533
      Payback
      16.9 years
      Net after 10 years
      -$3,670

      Cooling $454Heating $267Electricity used: 4,505 kWhSaved vs. a minimum-efficiency heat pump: $243

      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 2 ton models

      See all 331 2 ton central heat pumps, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of September 30, 2026. How we use the data.