The ton of cooling load can be calculated as: h = 500 (1 US gal/min) (10 oF) = 5000 Btu/h. = (5000 Btu/h) / (12000 Btu/ton) = 0.42 ton. Converting between heat and energy units. Converting kW/tonn to COP or EER. Air Conditioning - Air Conditioning systems - heating, cooling and dehumidification of indoor air for thermal comfort.