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Glossary · Fundamentals
Quick answer

A measure of AC/heat-pump capacity; 1 ton = 12,000 BTU/hr.

In HVAC, a 'ton' is a unit of cooling capacity equal to 12,000 BTU per hour — not a measure of weight. A 3-ton air conditioner can remove 36,000 BTU of heat per hour. The right tonnage for a home comes from a Manual J load calculation, not square footage.

Why Ton matters

Fundamental HVAC terms help you understand capacity, comfort, and whether a quote is based on your actual home instead of a rule of thumb. They are the language behind repair, replacement, and sizing decisions.

When you'll see this term

You will usually hear this term during diagnostics, system sizing, replacement estimates, and explanations of heating or cooling capacity.

Questions to ask your technician

  • How does this apply to my home's heating or cooling load?
  • Was this number measured, calculated, or estimated?
  • What changes if my insulation, windows, or ductwork are improved?
Go deeper

What size HVAC system do I need?

Related terms

BTU (British Thermal Unit)
The basic unit of heat energy used to measure HVAC capacity.
Manual J (Load Calculation)
The standard calculation that sizes HVAC equipment to a home.
SEER2 (Seasonal Energy Efficiency Ratio 2)
The cooling-efficiency rating for ACs and heat pumps — higher is better.
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