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      48,000 BTU mini-split heat pump · M series

      Lennox MLB048S4M-2P

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

      Ranks #55 of 146 48,000 BTU mini-splits for cooling efficiency, and costs about $1,256 a year to run in a mixed climate like Atlanta.

      SEER2
      21.8 Cooling efficiency over a season
      Average · beats 44%
      HSPF2
      9.8 Heating efficiency over a season
      Below average · beats 33%
      EER2
      11.7 Cooling efficiency on a 95°F day
      Below average · beats 16%
      Heat at 5°F
      45,000 BTU/h92% of its 47°F output
      Average · beats 48%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 45,000 BTU/h at 5°F.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • You mainly need heat - its HSPF2 is below average for mini-splits.
      • You want the newest refrigerant - it uses R-410A, which is being phased down.

      Calculate my running cost

      Details

      Specifications48,000 BTU, R-410A
      General
      BrandLennox
      Also sold asMidea, MDV, TRUST AIR CONDITIONERS, DIRECT AIR, CanAir, Elios, ECO-AIR, KERR, Custom Comfort, Senville, Kepler, Franklin
      Outdoor unit modelMLB048S4M-2P
      SeriesM series
      TypeMini-split heat pump
      Nominal size48,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-410A
      Connected (smart) capableNo
      On the market sinceDecember 18, 2019
      Last certifiedJune 25, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better21.8 (range 20.9-21.8)
      EER2Efficiency at 95°F outdoors11.7
      Cooling capacity47,000-48,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.0-9.8
      Capacity at 47°F49,000 BTU/h
      Capacity at 17°F36,000 BTU/h
      Capacity at 5°F42,500-45,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.00
      ENERGY STAR cold climateYes
      Heating output as it gets colder92% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its best matchup 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.
      - LENNOX · cold climate21.811.79.845,000207699107
      - LENNOX · cold climate21.411.79.443,500207699109
      - LENNOX · cold climate20.911.79.042,500207699108
      Same unit, other model numbers12

      These model numbers have exactly the same certified ratings and matchups as the Lennox MLB048S4M-2P: the same equipment under another brand, or a variant code for voltage, colour or market. Everything on this page applies to them.

      Yearly running cost in 10 large cities$1,029-$3,078

      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 MLB048S4M-2P?
      The Lennox MLB048S4M-2P is rated at up to 21.8 SEER2 and 11.7 EER2 for cooling and up to 9.8 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 20.9-21.8.
      Is the Lennox MLB048S4M-2P good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 45,000 BTU/h at 5°F with a COP of 2.00, so it is still 2.0 times as efficient as electric resistance heat at that temperature.
      How much does the Lennox MLB048S4M-2P cost to run per year?
      At its rated efficiency it costs about $1,029-$3,078 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,314 in Phoenix and $2,606 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Is the Lennox MLB048S4M-2P the same as the Midea MMCMHAQ48EA3?
      Yes, as far as the certified ratings go. ENERGY STAR lists 13 model numbers with identical efficiency, capacity and matchups, which means the same outdoor unit sold under a different brand or with a minor variant code (voltage, colour or region). The full list is on this page.
      What refrigerant does the Lennox MLB048S4M-2P use?
      It uses R-410A. R-410A is being phased down under the EPA AIM Act, and new systems are moving to R-454B and 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 $1,327/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 MLB048S4M-2P
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $1,327
      Current system, per year
      $2,474
      You save per year
      $1,147
      Payback
      15.7 years
      Net after 10 years
      -$6,532

      Cooling $767Heating $560Electricity used: 8,294 kWhSaved vs. a minimum-efficiency heat pump: $574

      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 June 25, 2026. How we use the data.