the torque draw of the compressor will be dependent on the compressor size, line size, system size, refrigerant used, temperature deltas, etc. the horsepower will be dependent on the torque required by the compressor, the clutch pulley size, the driver pulley size, and the engine RPM.
everything that is driven off the engine, or electrically draws power. however electrical draws are buffered by the battery to some extent.
between 1 and 5 hp is a rough rule of thumb, however as many people indicated - if you want AC, who cares how much hp is drawn.
