A 1,000 square foot home or apartment needs 1.5–2 tons (18,000–24,000 BTU) of air conditioning in most climates, with poorly insulated homes in hot regions requiring up to 2.5 tons (30,000 BTU). The baseline calculation is simple — 1,000 × 20 BTU/sq ft = 20,000 BTU — but your climate zone, insulation, ceiling height, and window exposure can shift that number by 30–50% in either direction.
At 1,000 sq ft, you're in the sweet spot where a single AC system handles the entire space efficiently. This guide gives you the exact tonnage for your specific conditions plus equipment recommendations and cost data.
AC Size for 1,000 Sq Ft by Climate Zone
| Climate Zone | Cities | Recommended BTU | Recommended Tonnage | Annual Cooling Cost (est.) |
|---|---|---|---|---|
| Zone 1 (Hot-Humid) | Miami, Key West | 25,000–30,000 | 2–2.5 ton | $550–$750 |
| Zone 2 (Hot) | Houston, Phoenix, Tampa | 22,000–28,000 | 2–2.5 ton | $450–$650 |
| Zone 3 (Warm) | Atlanta, Dallas, Charlotte | 20,000–25,000 | 1.5–2 ton | $350–$500 |
| Zone 4 (Mixed) | Nashville, St. Louis, DC | 18,000–22,000 | 1.5–2 ton | $250–$400 |
| Zone 5 (Cool) | Chicago, Denver, Boston | 16,000–20,000 | 1.5 ton | $200–$350 |
| Zone 6 (Cold) | Minneapolis, Milwaukee | 14,000–18,000 | 1.5 ton | $150–$250 |
Adjustment Factors for 1,000 Sq Ft Homes
Your specific home characteristics shift the baseline:
| Factor | Adjustment | Adjusted BTU for 1,000 Sq Ft |
|---|---|---|
| Baseline (Zone 4, average) | — | 20,000 BTU |
| Poor insulation (pre-1980) | +30% | 26,000 BTU |
| Good insulation (2015+ code) | −15% | 17,000 BTU |
| 9-foot ceilings | +12% | 22,400 BTU |
| 10-foot ceilings | +25% | 25,000 BTU |
| Top floor / upper level | +15% | 23,000 BTU |
| Basement level | −20% | 16,000 BTU |
| Large windows, sun-exposed | +15% | 23,000 BTU |
| Open kitchen included | +4,000 BTU | 24,000 BTU |
| Heavy shade, trees | −10% | 18,000 BTU |
| Leaky ductwork in attic | +20% | 24,000 BTU |
Sizing Examples for 1,000 Sq Ft
Example 1: 1,000 sq ft condo in Phoenix, AZ
Top floor, 9-ft ceilings, west-facing sliding glass doors, average insulation (2005 build), open kitchen.
- Base: 1,000 × 26 (Zone 2) = 26,000
- 9-ft ceilings: +12% = 29,120
- Top floor: +15% = 33,488
- West-facing glass: +15% = 38,511
- Kitchen: +4,000 = 42,511
- Dry climate: −10% = 38,260
Result: 38,260 BTU → 3.5-ton system. In a Phoenix top-floor unit with west-facing glass, even 1,000 sq ft demands serious cooling capacity. Window tinting or exterior blinds could reduce this by 5,000–8,000 BTU.
Example 2: 1,000 sq ft ranch in Indianapolis, IN
Single story, 8-ft ceilings, moderate windows, average insulation (1998), shaded by mature trees.
- Base: 1,000 × 20 (Zone 5) = 20,000
- Shade trees: −10% = 18,000
- Average ductwork: +0% = 18,000
Result: 18,000 BTU → 1.5-ton system. A well-shaded 1,000 sq ft home in a moderate climate is the easiest sizing scenario. A 1.5-ton system provides comfortable cooling with energy to spare.
Example 3: 1,000 sq ft new-build apartment in Austin, TX
Ground floor, 9-ft ceilings, above-code insulation (2024 build), ducts inside conditioned space, minimal windows.
- Base: 1,000 × 22 (Zone 2) = 22,000
- Excellent insulation: −20% = 17,600
- 9-ft ceilings: +12% = 19,712
- Ducts in conditioned space: −10% = 17,741
- Ground floor: −5% = 16,854
Result: 16,854 BTU → 1.5-ton system. Modern construction dramatically reduces cooling loads. This new Austin apartment needs the same tonnage as the shaded ranch in Indianapolis despite being in a much hotter climate.
System Options for 1,000 Sq Ft
| System Type | BTU Range | Installed Cost (2026) | SEER2 Range | Best For |
|---|---|---|---|---|
| Central AC (1.5 ton) | 18,000 | $3,500–$6,000 | 14–22 | Ducted homes |
| Central AC (2 ton) | 24,000 | $4,000–$6,500 | 14–22 | Hot climates, ducted |
| Mini split (single-zone) | 18,000–24,000 | $2,500–$4,500 | 18–33 | Open-plan, no ducts |
| Mini split (2-zone) | 18,000–24,000 | $4,000–$7,000 | 16–24 | Separated rooms |
| Window AC (2 units) | 10,000–12,000 each | $500–$1,000 total | 10–12 CEER | Budget, rental |
| Heat pump (1.5–2 ton) | 18,000–24,000 | $5,000–$8,000 | 16–22 | Heat + cool, efficiency |
For 1,000 sq ft, a single mini split or small central system is the most cost-effective approach. Avoid splitting into too many zones — a single 18,000 BTU unit serves an open 1,000 sq ft apartment better than three 6,000 BTU heads.
Monthly Cooling Cost for 1,000 Sq Ft
| System Efficiency | Monthly Cost (hot climate) | Monthly Cost (moderate climate) | Monthly Cost (cool climate) |
|---|---|---|---|
| SEER2 14 | $95–$130 | $55–$75 | $30–$50 |
| SEER2 18 | $75–$100 | $45–$60 | $25–$40 |
| SEER2 22 | $60–$85 | $35–$50 | $20–$30 |
| SEER2 26+ | $50–$70 | $30–$40 | $15–$25 |
Based on $0.15/kWh. Multiply by your local rate ÷ 0.15 for your costs.
Key Takeaways
- Most 1,000 sq ft homes need 1.5–2 tons (18,000–24,000 BTU) — a 3-ton or larger system is almost certainly oversized
- Climate zone and insulation quality are the two biggest variables at this size
- New construction (2020s code) may need only 1.5 tons even in warm climates due to improved insulation
- A single mini split or small central system is the most cost-effective approach — avoid over-zoning
- Monthly cooling costs typically run $30–$100 depending on climate and efficiency
- At 1,000 sq ft, the difference between SEER2 14 and 22 saves $20–$45/month — significant over 15 years
Frequently Asked Questions
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