The electrical network of the Pilatus PC-9M aircraft is analyzed in this paper. Measurements of electrical current and voltage from the power source were carried out in 5 flight modes: takeoff, climb, cruising, descent, and landing. Based on in-flight measurements, a load diagram of the aircraft power source was created and used in the analysis of the aircraft's electrical balance for two flights; one in normal operation and the other with all electrical consumers switched on. Furthermore, the impact of individual electrical consumers on battery autonomy in case of generator failure was analyzed. The obtained measured results were compared with theoretical calculations according to the prescribed procedure in case of generator failure based on data from the AFM and AMM. It was concluded that the difference in electrical consumption in different modes is relatively small, with the highest electrical consumption being during landing. Furthermore, at maximum load (night flying in icing conditions), electrical consumption is 44,8% higher than during normal daytime flying. Additionally, it has been proven that the autonomy of the aircraft electrical network in case of generator failure allows the pilot enough time for a safe landing, even in the worst conditions when the load on the power source is at its maximum.