Method for controlling the performance of a fan motor for a vacuum cleaner which has a replaceable filter bag arranged in a dust chamber, wherein - a differential pressure between a first region lying in the vacuum flow direction upstream of the replaceable filter bag and a second region lying in the vacuum flow direction downstream of the replaceable filter bag is detected and - the performance of the fan motor is adjusted as a function of the detected differential pressure, characterised in that - the differential pressure is measured with the aid of a differential pressure sensor and the performance to be adjusted is determined based on a functional relationship between the measured differential pressure and a performance to be adjusted, wherein the performance to be adjusted is determined with the aid of a stored characteristic curve which indicates the performance to be adjusted of the fan motor as a function of an average differential pressure for at least two different floor coverings on which the vacuum cleaner can be operated, or - a first negative pressure in the first region is measured by a first pressure sensor and a second negative pressure in the second region is measured by a second pressure sensor; as a function of the negative pressure in the first region a floor covering on which the vacuum cleaner is being operated is determined; the differential pressure is determined as a difference between the first and the second negative pressure; and the performance of the fan motor is adjusted as a function of the determined differential pressure and the determined floor covering; wherein the performance to be adjusted is determined with the aid of a stored characteristic curve. - a differential pressure between a first region lying in the vacuum flow direction upstream of the replaceable filter bag and a second region lying in the vacuum flow direction downstream of the replaceable filter bag is detected and - the performance of the fan motor is adjusted as a function of the detected differential pressure, - the differential pressure is measured with the aid of a differential pressure sensor and the performance to be adjusted is determined based on a functional relationship between the measured differential pressure and a performance to be adjusted, wherein the performance to be adjusted is determined with the aid of a stored characteristic curve which indicates the performance to be adjusted of the fan motor as a function of an average differential pressure for at least two different floor coverings on which the vacuum cleaner can be operated, or - a first negative pressure in the first region is measured by a first pressure sensor and a second negative pressure in the second region is measured by a second pressure sensor; as a function of the negative pressure in the first region a floor covering on which the vacuum cleaner is being operated is determined; the differential pressure is determined as a difference between the first and the second negative pressure; and the performance of the fan motor is adjusted as a function of the determined differential pressure and the determined floor covering; wherein the performance to be adjusted is determined with the aid of a stored characteristic curve.