The object of the work is Specific Fan Power. The first aim of the thesis was to compare SFP of two Air Handling Units with different type of control. SFP is the main value of regulating of energy consump-tion of the fan system. This fact indicates need of SFP controlling. The second aim of the thesis was to compare direct and indirect measurements of active power that are used for calculation of SFP. Incorrect method of measuring of active power can lead to wrong calculations of SFP.

The first part is theoretical description of calculation of SFP value. It shows what can influence SFP. Then measurements in A-building of Mikkeli University of Applied Science were made. Active powers were measured for four fans in two AHU by means of two methods. Then SFP values were calculated and compared with requirements.

As a main result, it was shown that direct measuring of active power do not lead to correct and reliable results. According to calculations and measurements that were done in this thesis SFP values of 3 fans are in normal range. Only one fan has poor SFP value and it is so because of belt connection that is in inappropriate condition.