Air Conditioning Term …. “Ton” 1 ton of capacityequals 12,000 Btu/hr … for 24 hours Background on the derivation for tons of refrigeration…and information on the similar SI standard The latent heat of fusion for ice is 144 BTU/lb. For one ton, that is 2000 lb x 144 BTU/lb, or 288,000 BTU. As a rule of thumb, 400 square feet can be cooled per 12,000 BTU/hr (12,000 BTU/hr equals one ton of air conditioning). However, other factors which will also affect the total heat load. • Simply put, a one-ton air conditioner can remove 12,000 BTU from a space per hour.