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      What size mini-split for 800 sq ft?

      Short answer: 24,000 BTU, depending on your climate and insulation. In a mixed climate like Atlanta: 24,000 BTU.

      By climate

      Average insulation, 8 ft ceilings, three occupants.

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      Work it out for your room

      Pre-filled with 800 sq ft. Pick your city and adjust insulation, sun and ceiling height.

      Your space
      Your climate
      Mini-split size
      24,000 BTU
      Central / ducted size
      2 ton
      Cooling load
      21,300 BTU/h
      Heating load
      12,000 BTU/h

      See 24,000 BTU mini-splitsSee 2-ton central heat pumps

      Rule-of-thumb estimate: cooling follows the ENERGY STAR room sizing table, heating uses typical BTU per square foot for the climate (NOAA 1991-2020 heating degree days). For a whole-house system, ask your installer for a Manual J load calculation.

      More detail

      Cooling and heating loads by climateBTU/h
      • Hot and dry (Phoenix)cooling 21,300 · heating 12,000
      • Hot and humid (Houston)cooling 21,300 · heating 12,000
      • Mixed (Atlanta)cooling 19,500 · heating 15,200
      • Cold (Chicago)cooling 18,600 · heating 21,600
      • Very cold (Minneapolis)cooling 16,800 · heating 24,000

      Cooling follows the ENERGY STAR sizing table; heating uses BTU per sq ft for the climate (NOAA 1991-2020 normals).

      How insulation changes the sizein Atlanta
      • Poor24,000 BTU · heating 19,800 BTU/h
      • Average24,000 BTU · heating 15,200 BTU/h
      • Good18,000 BTU · heating 12,200 BTU/h
      • Very good18,000 BTU · heating 9,900 BTU/h
      Top 5 24,000 BTU mini-splitsranked by SEER2
      #ModelSEER2EER2HSPF2COP at 5°F
      1SLIMAIR SHC24VH2AG27.514.314.52.10
      2Blueridge BXS6Z24UC0also sold as 6 other model numbers27.014.010.01.80
      3TOSOT TW24HAY32A1DO27.014.010.01.80
      4TOSOT TW24WH29D6DOalso sold as 1 other model number27.014.010.01.80
      5TOSOT TWH24AD32AOalso sold as 4 other model numbers27.014.010.01.80
      Questions3
      What size mini-split do I need for 800 square feet?
      About 24,000 BTU. In a mixed climate like Atlanta the estimate is 24,000 BTU (cooling load 19,500 BTU/h, heating load 15,200 BTU/h). Hot climates need more cooling capacity and cold climates more heating capacity, as the table shows.
      How many BTU do I need for 800 square feet?
      For cooling, roughly 21,300 BTU/h in a hot, dry climate and 16,800 BTU/h in a cold one. For heating, from 12,000 to 24,000 BTU/h depending on how cold winters get. Older, drafty homes need up to 30% more.
      Is it better to oversize or undersize a heat pump?
      Neither, but slight undersizing is usually less harmful for cooling. An oversized unit short-cycles and leaves the air clammy. In cold climates, size for the heating load and check the unit’s output at 5°F, or plan for backup heat on the coldest nights.

      Other sizes

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