Due to large number of bearing variations it is becoming increasingly important to know the exact characteristic of a bearing during its running time, especially in assemblies such as vacuum cleaner unit where rotational speed of electric motor can exceed 70000 rpm. This paper is describing the design process of a method for measuring power losses in bearings, since it is hard to determine values of power losses during different running periods with standard tests. Method used, was measurement of momentum on an outer ring of a bearing using force sensor and measurement of temperature with use of IR sensor. Introduced method does not include clutch, therefore higher range of rotational speeds is possible. Proposed method also provides better momentum measurement accuracy than standard tests at high rotational speeds. Findings of a 5 hour tests were that during running in start-up period power loses in 608 ball bearings range from 5 to 58 W, however in steady operational state power losses drop down to 3 to 26 W depending on bearing configuration. Temperatures of ball bearings were ranging from 45 to 80 °C also depending on bearing configuration.