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      9,000 BTU mini-split heat pump · M series

      Lennox MHB009S4S-1L

      Below average cooling and heating efficiency for a 9,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #296 of 395 9,000 BTU mini-splits for cooling efficiency, and costs about $264 a year to run in a mixed climate like Atlanta.

      SEER2
      21.5 Cooling efficiency over a season
      Below average · beats 39%
      HSPF2
      9.1 Heating efficiency over a season
      Below average · beats 13%
      EER2
      12.5 Cooling efficiency on a 95°F day
      Average · beats 44%
      Heat at 5°F
      7,000 BTU/h70% of its 47°F output
      Very good · beats 74%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 7,000 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.
      • 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

      Specifications9,000 BTU, R-410A
      General
      BrandLennox
      Outdoor unit modelMHB009S4S-1L
      SeriesM series
      TypeMini-split heat pump
      Nominal size9,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-410A
      Connected (smart) capableNo
      On the market sinceDecember 18, 2019
      Last certifiedApril 27, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better21.5 (range 21.5)
      EER2Efficiency at 95°F outdoors12.5
      Cooling capacity9,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.1
      Capacity at 47°F10,000 BTU/h
      Capacity at 17°F6,300 BTU/h
      Capacity at 5°F7,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.16
      ENERGY STAR cold climateYes
      Heating output as it gets colder70% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with MWHB009S4-*L 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.
      MWHB009S4-*L LENNOX · cold climate21.512.59.17,000211034461
      MWHB009S4 LENNOX · cold climate21.512.59.17,000210665648
      MWHB009S4-1L LENNOX · cold climate21.512.59.17,000208106641
      Yearly running cost in 10 large cities$199-$662

      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 MHB009S4S-1L?
      The Lennox MHB009S4S-1L is rated at up to 21.5 SEER2 and 12.5 EER2 for cooling and up to 9.1 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the Lennox MHB009S4S-1L good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 7,000 BTU/h at 5°F with a COP of 2.16, so it is still 2.2 times as efficient as electric resistance heat at that temperature.
      How much does the Lennox MHB009S4S-1L cost to run per year?
      At its rated efficiency it costs about $199-$662 a year in electricity in large U.S. cities, depending on climate and local rates - for example $263 in Phoenix and $567 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 MHB009S4S-1L?
      ENERGY STAR lists 3 certified combinations for this outdoor unit. The highest-rated ones use LENNOX MWHB009S4-*L, LENNOX MWHB009S4, LENNOX MWHB009S4-1L.
      What refrigerant does the Lennox MHB009S4S-1L 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 $270/yrYou save $210/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 MHB009S4S-1L
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $270
      Current system, per year
      $480
      You save per year
      $210
      Payback
      16.7 years
      Net after 10 years
      -$1,400

      Cooling $147Heating $123Electricity used: 1,690 kWhSaved vs. a minimum-efficiency heat pump: $100

      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.