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      48,000 BTU mini-split heat pump · MMLD Mini-Split

      Lennox MMLD048S6S-1P

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

      Ranks #79 of 146 48,000 BTU mini-splits for cooling efficiency, and costs about $1,331 a year to run in a mixed climate like Atlanta.

      SEER2
      20.0 Cooling efficiency over a season
      Below average · beats 18%
      HSPF2
      10.4 Heating efficiency over a season
      Average · beats 57%
      EER2
      12.2 Cooling efficiency on a 95°F day
      Below average · beats 33%
      Heat at 5°F
      54,000 BTU/h100% of its 47°F output
      Below average · beats 9%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 54,000 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 mini-splits.

      Calculate my running cost

      Details

      Specifications48,000 BTU, R-32
      General
      BrandLennox
      Outdoor unit modelMMLD048S6S-1P
      SeriesMMLD Mini-Split
      TypeMini-split heat pump
      Nominal size48,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-32
      Connected (smart) capableNo
      On the market sinceAugust 30, 2024
      Last certifiedApril 27, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better20.0 (range 18.0-20.0)
      EER2Efficiency at 95°F outdoors11.7-12.2
      Cooling capacity47,000-48,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.5-10.4
      Capacity at 47°F54,000 BTU/h
      Capacity at 17°F41,000-42,000 BTU/h
      Capacity at 5°F52,000-54,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80
      ENERGY STAR cold climateYes
      Heating output as it gets colder100% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with M33D048S6-1P at the standard test temperatures, in BTU/h:

      Certified matchups3 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.
      M33D048S6-1P LENNOX · cold climate20.012.210.454,000218214252
      MDDD048S6-1P LENNOX · cold climate18.011.79.554,000215810033
      MMD048S6-1P LENNOX · cold climate18.012.09.552,000216581335
      Yearly running cost in 10 large cities$1,131-$3,229

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

      Questions5
      What is the SEER2 rating of the Lennox MMLD048S6S-1P?
      The Lennox MMLD048S6S-1P is rated at up to 20.0 SEER2 and 12.2 EER2 for cooling and up to 10.4 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 18.0-20.0.
      Is the Lennox MMLD048S6S-1P 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 1.80, so it is still 1.8 times as efficient as electric resistance heat at that temperature.
      How much does the Lennox MMLD048S6S-1P cost to run per year?
      At its rated efficiency it costs about $1,131-$3,229 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,423 in Phoenix and $2,720 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 Lennox MMLD048S6S-1P?
      ENERGY STAR lists 3 certified combinations for this outdoor unit. The highest-rated ones use LENNOX M33D048S6-1P, LENNOX MDDD048S6-1P, LENNOX MMD048S6-1P.
      What refrigerant does the Lennox MMLD048S6S-1P use?
      It uses R-32.

      Running cost and savings

      Pre-filled with this model. Pick your city and what you heat with today; everything else is optional.

      Heat pump $1,426/yrYou save $1,147/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 Lennox MMLD048S6S-1P
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $1,426
      Current system, per year
      $2,573
      You save per year
      $1,147
      Payback
      15.7 years
      Net after 10 years
      -$6,532

      Cooling $845Heating $582Electricity used: 8,915 kWhSaved vs. a minimum-efficiency heat pump: $562

      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 April 27, 2026. How we use the data.