AC Tonnage Chart: What Size AC for Your Home?
AC Tonnage Chart by Home Size
Based on ASHRAE cooling load calculations for standard construction (R-13 walls, R-30 ceiling, double-pane windows). Moderate climate = Zone 3-4. Hot climate = Zone 1-2.
| Home Size | Moderate Climate | Hot Climate | BTU/h | Typical Cost (Installed) |
|---|---|---|---|---|
| 600–800 sq ft | 1.5 ton | 2 ton | 18,000–24,000 | $2,500–4,000 |
| 800–1,000 sq ft | 2 ton | 2.5 ton | 24,000–30,000 | $3,000–5,000 |
| 1,000–1,200 sq ft | 2 ton | 3 ton | 24,000–36,000 | $3,500–5,500 |
| 1,200–1,500 sq ft | 2.5 ton | 3.5 ton | 30,000–42,000 | $4,000–6,000 |
| 1,500–1,800 sq ft | 3 ton | 4 ton | 36,000–48,000 | $4,500–7,000 |
| 1,800–2,200 sq ft | 3.5 ton | 4.5 ton | 42,000–54,000 | $5,000–8,000 |
| 2,200–2,800 sq ft | 4 ton | 5 ton | 48,000–60,000 | $6,000–9,000 |
| 2,800–3,500 sq ft | 5 ton | 5 ton+ | 60,000+ | $7,000–12,000 |
Installed cost includes: outdoor condenser, indoor evaporator coil, basic ductwork modifications, thermostat, and labor. Does not include ductwork replacement ($3,000–8,000 additional if needed).
AC Tonnage Formula
For a quick estimate:
Tonnage = Floor Area (sq ft) ÷ Coverage Area per Ton
Where coverage area per ton depends on climate:
- Zone 1-2 (hot): 300–400 sq ft/ton
- Zone 3-4 (moderate): 400–600 sq ft/ton
- Zone 5-6 (cool): 600–800 sq ft/ton
Example: 1,800 sq ft in Atlanta (Zone 3) = 1,800 ÷ 500 = 3.6 tons → round up to 4 ton unit.
For precise sizing, use our AC size calculator which accounts for insulation, windows, orientation, and climate zone.
SEER Rating and Cost Comparison
Higher SEER = lower electricity bills. The 2023 US DOE minimum is SEER 15 (SEER2 14.3) for new central ACs in the South/Southwest.
| SEER Rating | 3-Ton Annual Cost* | vs SEER 14 Savings | Typical Unit Cost |
|---|---|---|---|
| 14 (minimum, legacy) | $1,100 | Baseline | $2,500–3,500 |
| 16 | $960 | $140/year | $3,000–4,500 |
| 18 | $855 | $245/year | $3,500–5,500 |
| 20 | $770 | $330/year | $4,500–7,000 |
| 25 | $615 | $485/year | $6,000–10,000 |
*Based on 3-ton unit, 1,500 cooling hours/year, $0.15/kWh. Actual costs vary by climate and electricity rates.
Common Mistakes
- Oversizing by 1-2 tons: The #1 mistake. Contractors often oversize to avoid complaints. Result: short-cycling, poor humidity control, higher bills
- Not replacing ductwork: Old ducts may be undersized for a new, larger unit. Duct sizing should match the AC tonnage
- Ignoring existing insulation: If you've upgraded insulation or windows since the original AC was installed, you may need a SMALLER replacement unit
- Focusing only on SEER: A SEER 25 unit in the wrong size performs worse than a SEER 16 unit in the right size. Size first, then optimize efficiency
Frequently Asked Questions
What ton AC do I need for 1,500 sq ft?
For 1,500 sq ft in a moderate climate: 2.5–3 tons (30,000–36,000 BTU). In hot climates: 3.5–4 tons. In well-insulated new homes: 2–2.5 tons.
How many tons of AC per square foot?
The general rule is 1 ton per 400–600 sq ft in moderate climates. In hot climates: 1 ton per 300–400 sq ft. In well-insulated new construction: 1 ton per 600–800 sq ft.
Is a 3 ton AC enough for 2,000 sq ft?
In moderate climates: yes, 3 tons is sufficient for 2,000 sq ft with standard insulation. In hot climates: you likely need 4 tons. In well-insulated new homes: 3 tons may even be oversized.