What Size Air Conditioner Do I Need?

What Size Air Conditioner Do I Need?

Picking AC size is about where you live, how your home is built, when it was built, and your windows/air-sealing. Use the BTU-per-square-foot guide below to get a solid estimate—then our Master HVAC Designer will help you lock it in (Manual J).

 

 

The Four Big Factors

  1. Geographic location (climate)

    • Hot/humid areas need more BTU/ft² than cool-summer regions.

  2. Insulation & air-sealing

    • Tight, well-insulated homes need less cooling.

  3. Year built (energy code era)

    • Newer homes generally have lower loads; older homes trend higher unless upgraded.

  4. Windows & glass area

    • Big west/south glass or single-pane windows drive loads up; low-E double/triple pane bring loads down.

 

 

BTU Per Square Foot Guide (Cooling)

Pick your climate band and home condition. Multiply by cooled square footage to estimate total BTU/hr (then divide by 12,000 to get tons).

Climate band

Tight / New (2000s+ or upgraded)

Typical (1980s–2010s)

Older / Leaky (pre-1980, minimal upgrades)

Hot & Humid (e.g., FL Gulf/Atlantic)

18–22 BTU/ft²

22–28

28–35

Warm (South/Sunbelt interior)

16–20

20–25

25–32

Moderate (Mid-Atlantic / coastal PNW)

14–18

18–23

23–30

Cool Summers (Upper Midwest/Northeast north)

12–16

16–20

20–26

Quick anchors:
 Twin Cities, MN (cool summers): most homes land 16–22 BTU/ft².
 SW Florida (hot & humid): many homes land 22–28 BTU/ft².

 

 

Fast Examples

Example A — Twin Cities, MN

  • 2,000 ft², 1998 home, average windows/insulation → ~18 BTU/ft²

  • Load ≈ 2,000 × 18 = 36,000 BTU/hr → 3.0 tons nominal

Example B — SW Florida (Lee County)

  • 2,000 ft², 2010 home, good windows/insulation → ~24 BTU/ft²

  • Load ≈ 2,000 × 24 = 48,000 BTU/hr → 4.0 tons nominal

 

 

Adjustments (fine-tune your number)

  • Windows & orientation: heavy west/south glass or single-pane +10–20%; low-E triple pane –5%

  • Ducts in hot attic: +10–15% (or plan duct upgrades/sealing)

  • Ceiling height: +3% per foot above 8 ft average

  • Air-sealing: drafty/leaky homes +10%; very tight homes –5%

  • Shading & color: light roof + shade trees –5%; dark roof, full sun +5–8%

  • Dehumidification priority (FL): consider variable-speed air handlers and correct CFM/ton to control humidity

 

 

Quick Size Chart (Typical Homes)

Use as a ballpark starting point; your final selection may shift with the adjustments above.

Cool-Summer Regions (e.g., MN) — Typical Homes

Cooled area

BTU target

Tonnage (≈ BTU ÷ 12,000)

1,200 ft²

20–26k

1.5–2.0 ton

1,600 ft²

26–32k

2.0–2.5 ton

2,000 ft²

32–40k

2.5–3.5 ton

2,400 ft²

38–46k

3.0–4.0 ton

Hot & Humid (e.g., SW Florida) — Typical Homes

Cooled area

BTU target

Tonnage (≈ BTU ÷ 12,000)

1,200 ft²

26–34k

2.0–3.0 ton

1,600 ft²

32–40k

2.5–3.5 ton

2,000 ft²

40–50k

3.5–4.0 ton

2,400 ft²

48–58k

4.0–5.0 ton

 

 

Don’t Forget Reality vs. Nameplate

  • Tons are nominal. Real (sensible) capacity varies with indoor CFM, outdoor temperature, coil match, and SEER2/EER2 ratings.

  • Ductwork matters. Undersized or leaky ducts ruin performance—fixing ducts can reduce required tonnage.

  • Manual J is the gold standard. We’ll help you get there quickly.

 

 

We’ll Size It With You (Free)

A Master HVAC Designer will review:

  • ZIP/climate, square footage, year built

  • Insulation/air-sealing levels

  • Window type/orientation & shading

  • Duct location/condition and ceiling heights

You receive:

  • A BTU & tonnage target tailored to your home

  • An AHRI-matched system list (condenser + coil/air handler + furnace)

  • Notes your installer will appreciate (CFM/ton, duct notes, line-set size, breakers)

 

 

Next Steps

  • Talk to a Designer (fast sizing help)

  • Shop Central AC & Heat Pumps

  • Email your home details (we’ll reply with a sizing summary)

Furnace.Direct is an equipment supplier. Final selection and installation must meet local codes/permits. For manufacturer parts warranty, follow brand registration and installation requirements.