CFM for 3-ton AC?
About 1,200 CFM using the 400 CFM per ton rule of thumb.
Window AC cost = (watts ÷ 1,000) × hours/day × days × $/kWh. A 900 W unit running 8 hr/day for 90 days adds meaningful summer kWh.
Use the calculator form above with your room size, system capacity, or appliance usage. Results update instantly in your browser — no data is sent to a server.
Concise answers for common searches — definitions, steps, and comparisons.
About 1,200 CFM using the 400 CFM per ton rule of thumb.
12,000 BTU/hr of cooling capacity equals one ton of refrigeration.
Window AC cost = (watts ÷ 1,000) × hours/day × days × $/kWh. A 900 W unit running 8 hr/day for 90 days adds meaningful summer kWh.
Formula
See calculator inputs and results panel for step-by-step math.Select imperial/metric, rectangle vs area, tons vs BTU, or usage presets as shown.
Type room dimensions, system tonnage, CFM, appliance watts, or electric rate.
Pick climate zone 1–5 and insulation quality for load-based calculators.
Use BTU/hr, tons, CFM, duct diameter, or seasonal cost in the results panel.
Copy results or share a link with your HVAC contractor or energy auditor.
Use Duct CFM, Duct Size, or Energy Cost calculators for a complete HVAC plan.
Input
20×15 ft · 8 ft ceiling · zone 3Output
≈ 7,500 BTU/hr cooling300 sq ft × 25 BTU/sq ft × average insulation × 1.0 height factor.
Input
2.5 tonsOutput
1,000 CFM2.5 × 400 CFM/ton = 1,000 CFM supply airflow rule of thumb.
Common real-world scenarios where this tool saves time.
12×15 ft room, zone 3, average insulation → ~9,000–11,000 BTU/hr cooling load.
2,000 sq ft home, zone 4 → ~3.5–4 tons cooling with average insulation.
3-ton system → 1,200 CFM target → 14" round trunk at 700 FPM velocity.
900 W unit, 8 hr/day, 90 days at $0.16/kWh → seasonal cost estimate for budgeting.
Step-by-step chains that connect related tools for common tasks.
From room BTU to duct airflow and diameter.
Compare portable appliance electricity spending.
| Watts | 8 hr/day × 30 days | Monthly cost |
|---|---|---|
| 600 W | 144 kWh | $23 |
| 900 W | 216 kWh | $35 |
| 1,200 W | 288 kWh | $46 |
Rule-of-thumb sizing is a starting point — ACCA Manual J is the industry standard.
Undersized ducts reduce efficiency and comfort even when tonnage is correct.
Include climate zone, insulation, ceiling height, and sun exposure — or request Manual J.
Check heating BTU/hr and balance point, not just cooling tons.
Compressors cycle — actual kWh may be lower than watts × hours suggests.
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kWh = (watts ÷ 1000) × hours/day × days; cost = kWh × your $/kWh rate — enter your label watts and usage pattern.
Typical room units: 500–1,500 W depending on BTU rating — check the nameplate or manual for rated input watts.
Use 30 days for a monthly bill estimate or 90 days for a summer cooling season.
Yes — higher setpoints and fewer run hours lower kWh; this calculator uses the hours you enter per day.
Higher efficiency (more BTU per watt) lowers watts for the same cooling — use actual measured or label watts when possible.
It estimates AC portion only — taxes, fixed charges, and other loads are not included.
Window AC wattage, hours, and electric rate for cost estimates remain on your device — EverydayTools does not send window-ac-cost calculator data remotely.
Estimates only — not professional HVAC or energy audit advice. Verify with a licensed contractor before purchasing equipment.
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Reviewed on 2026-06-28.
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Typical window unit: 500–1,500 W
30 for monthly, 90 for summer season