Glossary · Heating, cooling & ventilation
Ton (of cooling)
Also called: ton of refrigeration · tonnage · cooling ton
A unit of heating and cooling capacity: one ton equals 12,000 BTU per hour (3.5 kW), based on the cooling from melting a ton of ice in a day.
What it means
The term is based on the cooling effect of melting a ton of ice over a day. Capacity changes with outdoor temperature, so a heat pump's rated tonnage isn't what it delivers in deep cold; check its capacity at your design temperature.
Why it matters in an audit
Rules of thumb like 'one ton per 500 square feet' tend to oversize equipment; a proper load calculation sets the right tonnage.
Typical numbers
Reference values with their sources. Your energy advisor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| Definition (NIST) | 1 ton = 12,000 BTU/h = 3.517 kW | nist.gov ↗ |
| Rule of thumb vs. calculation (ACCA blog, 2016) | Contractor rules of 400–600 ft² per ton vs. an average of 1,431 ft² per ton across 40 Manual J calculations | hvac-blog.acca.org ↗ |
| Definition (NRCan) | A ton of cooling capacity is 3.5 kW or 12,000 Btu/h | natural-resources.canada.ca ↗ |