How to Calculate KW Requirements for Typical Heater 30 11 2015· The KW calculation to raise the temperature is as follows KWtotal = KWheat up KWmaintain KWheat up = [ M x Cp x ΔT x SF /3412]/t M = weight of the material in pounds Cp = Specific Heat see examples in the chart ΔT = difference between the process set point end temperature and the start temperature