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      18,000 BTU mini-split heat pump · M series

      Lennox MPC018S4S-1P

      Very good cooling efficiency and average heating efficiency for a 18,000 BTU mini-split heat pump, but not rated for cold climates.

      Ranks #123 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $444 a year to run in a mixed climate like Atlanta.

      SEER2
      23.5 Cooling efficiency over a season
      Very good · beats 70%
      HSPF2
      10.7 Heating efficiency over a season
      Average · beats 68%
      EER2
      12.4 Cooling efficiency on a 95°F day
      Below average · beats 36%
      Heat at 5°F
      13,000 BTU/h59% of its 47°F output
      Excellent · beats 93%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 70% of mini-splits.
      • You want steady temperatures and quiet running - the compressor varies its speed.
      • You want a choice of indoor units - 13 certified pairings.

      Think twice if…

      • You often see nights below 0°F - it is not cold-climate certified.
      • You want the newest refrigerant - it uses R-410A, which is being phased down.

      Calculate my running cost

      Details

      Specifications18,000 BTU, R-410A
      General
      BrandLennox
      Outdoor unit modelMPC018S4S-1P
      SeriesM series
      TypeMini-split heat pump
      Nominal size18,000 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 better23.5 (range 17.8-23.5)
      EER2Efficiency at 95°F outdoors11.7-12.5
      Cooling capacity16,000-18,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.3-10.7
      Capacity at 47°F19,000-20,000 BTU/h
      Capacity at 17°F12,000-14,900 BTU/h
      Capacity at 5°F11,300-13,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.02-2.40
      ENERGY STAR cold climateNo
      Heating output as it gets colder59% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with MWMC018S4-1P at the standard test temperatures, in BTU/h:

      Certified matchups13 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.
      MWMC018S4-1P LENNOX23.512.410.711,300207683499
      MWMC018S4-*P LENNOX23.512.410.711,300211034418
      MWMC018S4 LENNOX23.512.410.711,300210665605
      MCFB018S4-2P LENNOX23.012.59.913,000207683510
      MCFB018S4 LENNOX23.012.59.913,000210665617
      MCFB018S4-*P LENNOX23.012.59.913,000211034430
      M22A018S4-2P LENNOX20.512.510.412,700207683516
      M22A018S4-*P LENNOX20.512.510.412,700211034436
      M22A018S4 LENNOX20.512.510.412,700210665623
      MMDB018S4-2P LENNOX20.012.310.513,000207683505
      MMDB018S4-*P LENNOX20.012.310.513,000211034425
      MMDB018S4 LENNOX20.012.310.513,000210665612
      MMA018SM4-*P17.811.79.312,800212348044
      Yearly running cost in 10 large cities$362-$1,091

      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 MPC018S4S-1P?
      The Lennox MPC018S4S-1P is rated at up to 23.5 SEER2 and 12.4 EER2 for cooling and up to 10.7 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 13 certified matchups SEER2 ranges from 17.8-23.5.
      Is the Lennox MPC018S4S-1P good for cold climates?
      It is not cold-climate certified: none of its matchups meet the ENERGY STAR cold-climate criteria (a COP of at least 1.75 at 5°F among other limits). In places with frequent sub-zero nights, pick a cold-climate 18,000 BTU model.
      How much does the Lennox MPC018S4S-1P cost to run per year?
      At its rated efficiency it costs about $362-$1,091 a year in electricity in large U.S. cities, depending on climate and local rates - for example $463 in Phoenix and $925 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 MPC018S4S-1P?
      ENERGY STAR lists 13 certified combinations for this outdoor unit. The highest-rated ones use LENNOX MWMC018S4-1P, LENNOX MWMC018S4-*P, LENNOX MWMC018S4.
      What refrigerant does the Lennox MPC018S4S-1P 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 $468/yrYou save $476/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 MPC018S4S-1P
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $468
      Current system, per year
      $944
      You save per year
      $476
      Payback
      14.7 years
      Net after 10 years
      -$2,240

      Cooling $270Heating $199Electricity used: 2,928 kWhSaved vs. a minimum-efficiency heat pump: $258

      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.