Sizing & How HVAC Works

Tonnage, BTUs, SEER2, and AFUE in plain English — how systems get sized and what the ratings mean.

Guides

What Size HVAC Do I Need? Tons, BTUs & Sizing (2026)

Size it with one formula: conditioned sq ft × 20–30 BTU (cooling, by climate) ÷ 12,000 = tons. A 2,000 sq ft mixed-climate home needs about 4 tons and a 100k BTU furnace. Climate factors, envelope adjustments, and the math shown.

Updated July 10, 2026