Device for adjusting the operating pressure of an oil-injected compressor installation with a compressor element (2) driven by a motor (4) with an adjustable rotational speed and a control module (13), where the device (15) is provided with a controlled inlet valve (16) which is connected to the air inlet (5) and a blow-off mechanism (17) which can be closed by means of a blow-off valve (19), where the inlet valve (16), the blow-off valve (19) and the control module (13) are electrically controllable components which are connected to an electronic control unit (22) for adjusting the operating pressure (Pw), which is measured by an operating pressure sensor (23).