Energy saving is an action to reduce the amount of energy use, but in its implementation without reducing the benefits to be obtained just use less energy. In an effort to save electricity in the building one way is to conduct an energy audit. The energy audit in the building is carried out in order to find out the intensity value of the consumption of electrical energy used in the building. In an effort to save electricity this time the object of research was the F5 building of Muhammadiyah University of Yogyakarta, in conducting research data collection was carried out on lighting systems, namely lamps and air conditioning systems, namely Air Conditioning (AC), area of space, and time of use of the room. The data is used to find the value of the Energy Consumption Intensity (IKE) in the building and then calculate the Energy Saving Opportunity and the cost of the electricity bill. Furthermore, the calculation of the use of electrical energy in LED lights and the comparison of the type of AC change into an AC inverter that is more energy efficient. The calculation results show that the use of electrical energy in lighting loads and AC air conditioners before replacing the AC inverter in building F5 is 7163,93 kWh in a month. Whereas after using an AC inverter, it was 5311.46 kWh in a month. The amount of electricity saving is 1852,47 kWh / month or 25%. The payback period or the return period of investment if the type of AC to AC Inverter is replaced is 5.3 years.