A laboratory scale-spray dryer performance was evaluated experimentally. Powder yield, drying rate, feeding rate, drying time, evaporation rate and energy consumption were investigated under different inlet air temperatures and atomization speeds for drying some milk-juice blends and whole milk. Theoretical approach of the dryer was developed, and energy inputs and outputs were estimated at the same experimental conditions. The results showed that the powder yield decreased with increasing both inlet air temperature and atomization speed, on the other hand, drying rate and time, feeding rate, evaporation rate increased with increasing both air temperature and atomization speed. Energy consumption decreased with increasing both air temperature and atomization speed, where, it ranged from 36.47 to 53.29 GJ/kg for the milk-juice blends depending on both atomization speed and drying temperature, while it ranged from 38.53 to 45.70 GJ/kg for the whole milk. Dryer efficiency increased with increasing drying temperature and atomization speed. It ranged from 42.09 to 71.03% depending on drying temperature and atomization speed. Theoretical approach showed that the estimated energy consumption was lower than the actual energy consumed, also, the estimated energy inputs were higher by 4.28 to 5.59% than the outputs of energy.