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      18,000 BTU mini-split heat pump · LEA SERIES

      NOVAIR LEA18SZ25SK-O

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

      Ranks #80 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $439 a year to run in a mixed climate like Atlanta.

      SEER2
      24.0 Cooling efficiency over a season
      Very good · beats 75%
      HSPF2
      10.8 Heating efficiency over a season
      Very good · beats 71%
      EER2
      13.5 Cooling efficiency on a 95°F day
      Very good · beats 74%
      Heat at 5°F
      12,800 BTU/h71% of its 47°F output
      Excellent · beats 96%

      A good fit if…

      • You want low cooling bills - its SEER2 beats 75% of mini-splits.
      • Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 12,800 BTU/h at 5°F.
      • It will heat most of the year - its HSPF2 beats 71% of mini-splits.
      • You want steady temperatures and quiet running - the compressor varies its speed.

      Think twice if…

      • 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
      BrandNOVAIR
      Outdoor unit modelLEA18SZ25SK-O
      SeriesLEA 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 sinceJanuary 1, 2023
      Last certifiedJune 13, 2026
      Cooling
      SEER2Seasonal efficiency, higher is better24.0 (range 23.5-24.0)
      EER2Efficiency at 95°F outdoors12.5-13.5
      Cooling capacity18,000 BTU/h
      Heating
      HSPF2Seasonal efficiency, higher is better10.5-10.8
      Capacity at 47°F18,000-19,000 BTU/h
      Capacity at 17°F14,100-14,900 BTU/h
      Capacity at 5°F11,300-12,800 BTU/h
      COP at 5°F2.0 = twice as efficient as a space heater2.02-2.44
      ENERGY STAR cold climateYes
      Heating output as it gets colder71% kept at 5°F

      Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with LEA18UUSK-I at the standard test temperatures, in BTU/h:

      Certified matchups2 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.
      LEA18UUSK-I · cold climate24.013.510.512,800207526951
      2LEA18UUSK-I23.512.510.811,300211709679
      Yearly running cost in 10 large cities$355-$1,079

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

      Questions5
      What is the SEER2 rating of the NOVAIR LEA18SZ25SK-O?
      The NOVAIR LEA18SZ25SK-O is rated at up to 24.0 SEER2 and 13.5 EER2 for cooling and up to 10.8 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 2 certified matchups SEER2 ranges from 23.5-24.0.
      Is the NOVAIR LEA18SZ25SK-O good for cold climates?
      Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 12,800 BTU/h at 5°F with a COP of 2.44, so it is still 2.4 times as efficient as electric resistance heat at that temperature.
      How much does the NOVAIR LEA18SZ25SK-O cost to run per year?
      At its rated efficiency it costs about $355-$1,079 a year in electricity in large U.S. cities, depending on climate and local rates - for example $455 in Phoenix and $915 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 NOVAIR LEA18SZ25SK-O?
      ENERGY STAR lists 2 certified combinations for this outdoor unit. The highest-rated ones use LEA18UUSK-I, 2LEA18UUSK-I.
      What refrigerant does the NOVAIR LEA18SZ25SK-O 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 $461/yrYou save $483/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 NOVAIR LEA18SZ25SK-O
      3. What it replaces
      4. Price replace the example with your quote
      Heat pump, per year
      $461
      Current system, per year
      $944
      You save per year
      $483
      Payback
      14.5 years
      Net after 10 years
      -$2,165

      Cooling $264Heating $197Electricity used: 2,881 kWhSaved vs. a minimum-efficiency heat pump: $266

      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.