26/12/2017 · wattage = the rated power of the fan motors (Watts) 1000 = convert from watts to kw. In this cold room evaporator we’ll be using 3 fans rated at 200W each and estimate that they will be running for 14 hours per day. Calculation: Q = fans x time x wattage / 1000. Q = 3 x 14 hours x 200W /