HVAC Rated
    Menu

      12,000 BTU mini-split heat pump · MWHD Mini-Split

      Lennox MWHD012S6S-1P

      Very good cooling efficiency and below average heating efficiency for a 12,000 BTU mini-split heat pump, but not rated for cold climates.

      Ranks #196 of 394 12,000 BTU mini-splits for cooling efficiency, and costs about $319 a year to run in a mixed climate like Atlanta.

      SEER2
      24.0 Cooling efficiency over a season
      Very good · beats 75%
      HSPF2
      9.0 Heating efficiency over a season
      Below average · beats 10%
      EER2
      13.3 Cooling efficiency on a 95°F day
      Very good · beats 70%
      Heat at 5°F
      8,000 BTU/h67% of its 47°F output
      Below average · beats 2%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 75% of mini-splits.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • You often see nights below 0°F - it is not cold-climate certified.
      • You mainly need heat - its HSPF2 is below average for mini-splits.

      Calculate my running cost

      Details

      Specifications12,000 BTU, R-32
      General
      BrandLennox
      Outdoor unit modelMWHD012S6S-1P
      SeriesMWHD Mini-Split
      TypeMini-split heat pump
      Nominal size12,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-32
      Connected (smart) capableNo
      On the market sinceJuly 5, 2024
      Last certifiedMarch 26, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better24.0 (range 24.0)
      EER2Efficiency at 95°F outdoors13.3
      Cooling capacity12,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.0
      Capacity at 47°F12,000 BTU/h
      Capacity at 17°F10,900 BTU/h
      Capacity at 5°F8,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.76
      ENERGY STAR cold climateNo
      Heating output as it gets colder67% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with MWHD012S6-1P at the standard test temperatures, in BTU/h:

      Certified matchups1 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.
      MWHD012S6-1P LENNOX24.013.39.08,000216411316
      Yearly running cost in 10 large cities$238-$801

      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 MWHD012S6S-1P?
      The Lennox MWHD012S6S-1P is rated at up to 24.0 SEER2 and 13.3 EER2 for cooling and up to 9.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
      Is the Lennox MWHD012S6S-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 12,000 BTU model.
      How much does the Lennox MWHD012S6S-1P cost to run per year?
      At its rated efficiency it costs about $238-$801 a year in electricity in large U.S. cities, depending on climate and local rates - for example $316 in Phoenix and $687 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 MWHD012S6S-1P?
      ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses LENNOX MWHD012S6-1P.
      What refrigerant does the Lennox MWHD012S6S-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 $325/yrYou save $293/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 MWHD012S6S-1P
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $325
      Current system, per year
      $619
      You save per year
      $293
      Payback
      15.3 years
      Net after 10 years
      -$1,566

      Cooling $176Heating $149Electricity used: 2,033 kWhSaved vs. a minimum-efficiency heat pump: $149

      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 12,000 BTU models

      See all 394 12,000 BTU mini-splits, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of March 26, 2026. How we use the data.