Furnace AC BTU Sizing — What Size Air Conditioner Do You Need?
Published: July 23, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC
Quick AC Size Guide
Small home under 1,200 sq ft: 1.5-2 tons (18,000-24,000 BTU). Medium 1,200-2,000 sq ft: 2-2.5 tons (24,000-30,000 BTU). Large 2,000-2,800 sq ft: 2.5-3 tons (30,000-36,000 BTU). Extra large over 2,800 sq ft: 3-4 tons (36,000-48,000 BTU). These are estimates — a Manual J calculation provides the precise size.
Why Oversizing Is Bad for AC
Unlike furnaces where oversizing causes short-cycling (which mainly wastes energy), AC oversizing causes both short-cycling AND poor dehumidification. An oversized AC cools the air quickly but does not run long enough to remove humidity — leaving the home cool but clammy. Proper AC sizing is critical for Vancouver humid summer conditions.
The Manual J Process
A Manual J load calculation measures: square footage, ceiling height, window size and type, insulation levels, building orientation, air leakage, number of occupants, and major appliances. The result is the precise cooling load in BTUs. Always insist on a Manual J before purchasing AC — it ensures the right size for your specific home.