Ton (Cooling Capacity)
A unit of cooling capacity equal to 12,000 BTU/h — roughly the melt rate of a ton of ice per day. Residential systems typically run 1.5–5 tons. The right tonnage comes from a Manual J load calculation, not from matching whatever size was there before.
The longer answer
One ton = 12,000 BTU/h of cooling capacity. A 3-ton system removes 36,000 BTU/h at rated conditions. But rated conditions (95°F outdoor) rarely match Seattle's summer peaks — which is why Manual J uses local design temperatures, not national averages.
Oversizing in tons is the most common sizing error: a 4-ton system in a home that needs 2.5 tons will cool the thermostat quickly but short-cycle, leaving humidity behind and creating temperature swings. The right tonnage is always the calculated load, never the next size up 'for good measure.'
The Seattle angle
Seattle's mild summer design temperatures often produce 2–3 ton recommendations for typical homes — smaller than Sun Belt sizing and another reason right-sizing matters here.
Where this decision happens
Nearby in the glossary
Ready for comfort you can count on?
Whether it's a furnace that quit on a cold morning or a whole new system, the Glendale team is ready. Honest pricing, expert work, and 87+ years behind every visit.
Hours & Emergency
- Mon–Sat: 8:00 AM – 7:00 PM
- Sun: Emergency On-Call Only
- Emergency line: (206) 243-7700