Central AC Sizing: Tonnage, SEER & Cost Guide
Quick Answer: Central AC is sized by cooling load in tons (1 ton = 12,000 BTU/h). An HVAC contractor performs an ACCA Manual J calculation considering floor area, i...
Central AC Sizing by House Size
| House Size | Tonnage | BTU/h | Duct Size (Main Trunk) |
|---|---|---|---|
| 800–1,200 sq ft | 1.5–2 ton | 18,000–24,000 | 10–12 inch |
| 1,200–1,500 sq ft | 2–2.5 ton | 24,000–30,000 | 12–14 inch |
| 1,500–2,000 sq ft | 2.5–3.5 ton | 30,000–42,000 | 14–16 inch |
| 2,000–2,500 sq ft | 3–4 ton | 36,000–48,000 | 16–18 inch |
| 2,500–3,500 sq ft | 4–5 ton | 48,000–60,000 | 18–20 inch |
Common Mistakes
- Oversizing "just in case": Leads to short-cycling, poor humidity control, and higher bills
- Ignoring insulation upgrades: If you've improved insulation, you may need a smaller unit
- Not considering duct condition: Leaky ducts can reduce effective capacity by 20–30%
Frequently Asked Questions
How is central AC sized?
Central AC is sized by cooling load in tons (1 ton = 12,000 BTU/h). An HVAC contractor performs an ACCA Manual J calculation considering floor area, insulation, windows, climate zone, and internal loads.
What SEER rating should I get?
Minimum SEER 15 (SEER2 14.3) required for new installations in the US South. SEER 16–18 offers the best value for most homes. SEER 20+ is worth it in hot climates with high electricity rates.
How long does a central AC last?
15–20 years with proper maintenance. Annual maintenance (filter changes, coil cleaning, refrigerant check) extends lifespan and maintains efficiency.
Disclaimer: Sizing estimates are preliminary. Final equipment selection should use ACCA Manual J load calculation by a licensed HVAC contractor.