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      18,000 BTU mini-split heat pump · UPAC

      Guardian UPC18CN23STG1

      Below average cooling efficiency and average heating efficiency for a 18,000 BTU mini-split heat pump, and certified for cold climates.

      Ranks #333 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $466 a year to run in a mixed climate like Atlanta.

      SEER2
      21.0 Cooling efficiency over a season
      Below average · beats 30%
      HSPF2
      10.0 Heating efficiency over a season
      Average · beats 43%
      EER2
      12.0 Cooling efficiency on a 95°F day
      Below average · beats 25%
      Heat at 5°F
      18,000 BTU/h100% 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 18,000 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.

      Calculate my running cost

      Details

      Specifications18,000 BTU, R-454B
      General
      BrandGuardian
      Also sold asColeman, Luxaire
      Outdoor unit modelUPC18CN23STG1
      SeriesUPAC
      TypeMini-split heat pump
      Nominal size18,000 BTU
      CompressorVariable-speed units run longer at low powerContinuously variable
      RefrigerantR-454B
      Connected (smart) capableNo
      On the market sinceSeptember 25, 2024
      Last certifiedMarch 9, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better21.0 (range 19.0-21.0)
      EER2Efficiency at 95°F outdoors11.7-12.0
      Cooling capacity18,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better9.0-10.0
      Capacity at 47°F18,000 BTU/h
      Capacity at 17°F13,200-14,100 BTU/h
      Capacity at 5°F18,000 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater1.80-2.00
      ENERGY STAR cold climateYes
      Heating output as it gets colder100% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with UNI18HW23STG1 at the standard test temperatures, in BTU/h:

      Certified matchups9 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.
      UNI18HW23STG1 GUARDIAN · cold climate21.012.010.018,000215743600
      UNI18HW23STG1 Coleman · cold climate21.012.010.018,000216572159
      UNI18HW23STG1 LUXAIRE · cold climate21.012.010.018,000216572170
      UNI18CS23STG1 GUARDIAN · cold climate20.012.010.018,000216019852
      UNI18CS23STG1 Coleman · cold climate20.012.010.018,000216566108
      UNI18CS23STG1 LUXAIRE · cold climate20.012.010.018,000216566110
      UNI18DT23STG1 GUARDIAN · cold climate19.011.79.018,000216445265
      UNI18DT23STG1 Coleman · cold climate19.011.79.018,000216566112
      UNI18DT23STG1 LUXAIRE · cold climate19.011.79.018,000216566114
      Yearly running cost in 10 large cities$404-$1,125

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

      Questions5
      What is the SEER2 rating of the Guardian UPC18CN23STG1?
      The Guardian UPC18CN23STG1 is rated at up to 21.0 SEER2 and 12.0 EER2 for cooling and up to 10.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 9 certified matchups SEER2 ranges from 19.0-21.0.
      Is the Guardian UPC18CN23STG1 good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 18,000 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 Guardian UPC18CN23STG1 cost to run per year?
      At its rated efficiency it costs about $404-$1,125 a year in electricity in large U.S. cities, depending on climate and local rates - for example $504 in Phoenix and $945 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 Guardian UPC18CN23STG1?
      ENERGY STAR lists 9 certified combinations for this outdoor unit. The highest-rated ones use GUARDIAN UNI18HW23STG1, Coleman UNI18HW23STG1, LUXAIRE UNI18HW23STG1.
      What refrigerant does the Guardian UPC18CN23STG1 use?
      It uses R-454B.

      Running cost and savings

      Pre-filled with this model. Pick your city and what you heat with today; everything else is optional.

      Heat pump $503/yrYou save $425/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 Guardian UPC18CN23STG1
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $503
      Current system, per year
      $928
      You save per year
      $425
      Payback
      16.5 years
      Net after 10 years
      -$2,752

      Cooling $302Heating $202Electricity used: 3,146 kWhSaved vs. a minimum-efficiency heat pump: $209

      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 18,000 BTU models

      See all 465 18,000 BTU mini-splits, ranked

      Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of March 9, 2026. How we use the data.