The #1 HVAC Mistake: Why Bigger Is NOT Better
An oversized AC unit cools fast but creates humidity, mold, and $500+/year in wasted energy.
When an HVAC system is too large for the space, it short-cycles: it reaches the thermostat temperature quickly, shuts off, then restarts minutes later. This constant on-off cycling wastes energy, fails to dehumidify (the coils never run long enough to remove moisture), and wears out the compressor years early.
How to Size Correctly
HVAC capacity is measured in tons (1 ton = 12,000 BTU/hour). The general rule is 1 ton per 500-600 square feet in moderate climates, but this varies significantly based on insulation, window count, ceiling height, climate zone, and sun exposure. A proper Manual J calculation by a qualified HVAC contractor accounts for all these factors — never accept a contractor who sizes by square footage alone.
Signs Your System Is Oversized
The house feels clammy or humid even when cool. The system runs for less than 10 minutes per cycle. Some rooms are too cold while others are warm. Your energy bills are higher than neighbors with similar homes. If you experience these symptoms, adding a dehumidifier helps, but the real fix is proper sizing at replacement time.