In Cotobie substation there are three transformers with a voltage levels of 132/45/15, 132/15/ and 132/33 from these the one with voltage level 132/45/15 is not working at this time. The total caring capacity of two transformer (132/15, 132/33) are 47.5MVA from this the 15 kV network is operated as radials and the total capacity of 132/15 kV transformer is 31.5 MVA supply to five 15 kV outgoing feeders and 132/33 KV transformer rating is 16MVA. Collecting of power transformer data, inspection of the MV distribution lines and distribution transformers, and digitizing the collected data in Wind-mil Software for making load simulation. Distribution total energy performance has been assessed thoroughly in Ethiopian Electric Utility using on data collected from Energy management and Billing processing departments. The analyzed and calculated energy in the budget year of 2020 total billed energy is 13,845.95GWH, out of this 10,352.48GWH is sold energy and 3,495.47GWH is aggregated energy losses (commercial and technical). This energy analyzed simply using collected data from billed energy not taken from substation energy meters but its data collected from Energy management and Billing processing departments. But the analyzed and assessed of technical energy load loss using Wind -Mil software is carried out in Cotobie Substation power distribution feeder‟s lines. In 2020 have been introduced 393,763KWH and annual revenue loss is 477,240.756 ETB birr.