The 150KV Wates Substation is the Substation in Kulon Progo district, Wates sub-district which supplies electrical energy in the Kulon Progo area, one of which is supply in the NYIA area (New Yogyakarta International Airport) which is a new airport project which is estimated to require around 20MW of electricity if there is an excess load capacity on the power transformer at the 150KV Wates substation, it will require an estimated peak load in the next few years to prevent this The estimated peak load of the power transformer in the 150KV Wates Substation in the next few years can be predicted using the backpropagation Artificial Neural Network method. Backpropagation Artificial Neural Network is an artificial intelligence system with the ability to learn and gather knowledge of learning outcomes in its cell network (neurons) so as to enable the network as a whole to be more intelligent in responding to input / input given. The ability to learn and accumulate this knowledge allows artificial neural network systems to be able to adapt to the environment that provides input to it. Like the human brain in response to different environmental conditions, the role of ANN in the field of research and development is very important in the future that demands aspects of automation and interactive aspects as well as aspects of speed between tools and humans. The estimated peak load of the power transformer is based on growth in energy consumption and economic growth and population growth while the data used are historical data from 2014 to 2018 which are then processed into input data to estimate the peak load of power transformers at 150KV Wates substations using backpropagation neural network method.