Recommended AC Size
3.5 Ton
BTU Capacity
42,000
Annual Cost
$315
Efficiency
Good
3.5 Ton
42,000
$315
Good
Get free quotes from HVAC professionals near you
We may earn a commission when you request quotes, at no extra cost to you.
Showing results for your area
Get free quotes from HVAC professionals near you
We may earn a commission when you request quotes, at no extra cost to you.
Showing results for your area
As an Amazon Associate, we earn from qualifying purchases.
Price as of Jul 24, 2026. Product prices and availability are accurate as of the date indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Inputs
Result
Base = 1,500/600 = 2.5 tons. ×1.0 climate ×1.1 age ×1.1 duct = 3.03. Windows (8, only 2 above 6, not enough for +0.1). Rounds to 3.0 ton standard size.
Inputs
Result
Base = 2,500/600 = 4.17. ×1.3 climate ×1.25 age ×1.25 duct = 8.47. +0.5 for 2nd story. +0.2 for windows above 6. Rounds to max 5.0 ton standard unit.
A general rule is 1 ton of AC per 600 square feet in a moderate climate. A 1,500 sq ft home needs about 2.5 tons. Hot climates need more (1 ton per 450 sq ft) while cool climates need less (1 ton per 700 sq ft).
| Home Size | Cool Climate | Moderate Climate | Hot Climate |
|---|---|---|---|
| 1,000 ft² | 1.5 tons | 1.5–2.0 tons | 2.0–2.5 tons |
| 1,500 ft² | 2.0 tons | 2.5 tons | 3.0–3.5 tons |
| 2,000 ft² | 2.5–3.0 tons | 3.0–3.5 tons | 4.0 tons |
| 2,500 ft² | 3.0–3.5 tons | 3.5–4.0 tons | 4.5–5.0 tons |
| 3,000 ft² | 3.5–4.0 tons | 4.0–5.0 tons | 5.0+ tons |
The federal minimum is 13-14 SEER depending on region. A 16 SEER unit offers good efficiency at reasonable cost. Units rated 20+ SEER provide the lowest operating costs but have higher upfront prices. In hot climates, higher SEER pays back faster.
| SEER Rating | Efficiency Class | Annual Cost (3-ton) | Best For |
|---|---|---|---|
| 13–14 | Minimum | $480–$520 | Budget installs, mild climates |
| 16 | Good | $390–$420 | Best value for most homes |
| 18–20 | High | $310–$350 | Hot climates, long-term savings |
| 21–25+ | Premium | $240–$290 | Max savings, eco-conscious |
Older homes (25+ years) typically need 25% more cooling capacity due to less insulation, single-pane windows, and air leaks. Homes under 10 years old with modern building codes need the baseline calculation with no added capacity.
| Home Age | Sizing Multiplier | Typical Insulation | Common Issues |
|---|---|---|---|
| Under 10 years | 1.0× | R-13+ walls, R-38+ attic | None—meets modern codes |
| 10–25 years | 1.1× | R-11 walls, R-19 attic | Some air leaks, aging seals |
| 25–50 years | 1.25× | R-4 to R-11 walls | Poor seals, single-pane windows |
| 50+ years | 1.3–1.4× | Minimal or none | No vapor barrier, balloon framing |
Leaky ducts can waste 20-30% of conditioned air, requiring a larger AC unit to compensate. Sealing ducts is often more cost-effective than upsizing the AC. New sealed ductwork operates at full efficiency with no added capacity needed.
The most common residential AC sizes are 2.5 to 3.5 tons (30,000-42,000 BTU). A 3-ton unit (36,000 BTU) fits most 1,500-2,000 sq ft homes in moderate climates. Larger homes or hot climates may need 4-5 ton units.
| AC Size | BTU/hr | Typical Home Size | Avg. Install Cost |
|---|---|---|---|
| 1.5 tons | 18,000 | 600–900 ft² | $3,000–$4,500 |
| 2.0 tons | 24,000 | 900–1,200 ft² | $3,500–$5,000 |
| 2.5 tons | 30,000 | 1,200–1,500 ft² | $3,800–$5,500 |
| 3.0 tons | 36,000 | 1,500–2,000 ft² | $4,000–$6,000 |
| 3.5 tons | 42,000 | 2,000–2,500 ft² | $4,500–$6,500 |
| 5.0 tons | 60,000 | 2,500–3,500 ft² | $5,500–$8,000 |
Read our guide
Read our guide
Read our guide
Calculate insulation R-values
Calculate electrical capacity
Calculate room square footage
Calculate materials for your building projects
Last Updated: Jul 24, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.
