A method allows for controlling the amount of electric current from an electrical circuit used by an electric motor in an electric motor driven reciprocating air compressor unit. A piston is reciprocated with a portable electric motor while air is channeled through an inlet into a compression cylinder, allowing the piston to draw on compressed amounts of air during each reciprocation. A valve mechanism is mounted to the inlet and is adjustable to a plurality of positions, each position allowing for one of a plurality of predeterminable amounts of air to be permitted to be drawn into the compression cylinder and compressed. The valve mechanism is manually adjusted to control the amount of air drawn into the compression cylinder and compressed by the piston to control the amount of electric current used by the electric motor.