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      42,000 BTU mini-split heat pump · SIERRA

      OLMO OS-MSR42-230VO

      Below average cooling and heating efficiency for a 42,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #50 of 61 42,000 BTU mini-splits for cooling efficiency, and costs about $1,189 a year to run in a mixed climate like Atlanta.

      SEER2
      20.0 Cooling efficiency over a season
      Below average · beats 18%
      HSPF2
      9.0 Heating efficiency over a season
      Below average · beats 7%
      EER2
      10.5 Cooling efficiency on a 95°F day
      Below average · beats 6%
      Heat at 5°F
      36,000 BTU/h86% of its 47°F output
      Below average · beats 18%

      A good fit if…

      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 36,000 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

      Specifications42,000 BTU, R-410A
      General
      BrandOLMO
      Also sold asComfiAire
      Outdoor unit modelOS-MSR42-230VO
      SeriesSIERRA
      TypeMini-split heat pump
      Nominal size42,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-410A
      Connected (smart) capableNo
      On the market sinceAugust 8, 2024
      Last certifiedJune 13, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better20.0 (range 20.0)
      EER2Efficiency at 95°F outdoors10.5
      Cooling capacity42,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.0
      Capacity at 47°F42,000 BTU/h
      Capacity at 17°F27,000 BTU/h
      Capacity at 5°F36,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.84
      ENERGY STAR cold climateYes
      Heating output as it gets colder86% 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 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.
      - · cold climate20.010.59.036,000215387338
      Same unit, other model numbers1

      These model numbers have exactly the same certified ratings and matchups as the OLMO OS-MSR42-230VO: 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$991-$2,902

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

      Questions5
      What is the SEER2 rating of the OLMO OS-MSR42-230VO?
      The OLMO OS-MSR42-230VO is rated at up to 20.0 SEER2 and 10.5 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 OLMO OS-MSR42-230VO good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 36,000 BTU/h at 5°F with a COP of 1.84, so it is still 1.8 times as efficient as electric resistance heat at that temperature.
      How much does the OLMO OS-MSR42-230VO cost to run per year?
      At its rated efficiency it costs about $991-$2,902 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,256 in Phoenix and $2,451 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
      Is the OLMO OS-MSR42-230VO the same as the ComfiAire CA5-42UMTO?
      Yes, as far as the certified ratings go. ENERGY STAR lists both 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 OLMO OS-MSR42-230VO 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 $1,265/yrYou save $901/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 OLMO OS-MSR42-230VO
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $1,265
      Current system, per year
      $2,166
      You save per year
      $901
      Payback
      17.8 years
      Net after 10 years
      -$6,992

      Cooling $739Heating $526Electricity used: 7,905 kWhSaved vs. a minimum-efficiency heat pump: $396

      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 13, 2026. How we use the data.