Soekarno-Hatta Airport Railink Project is one of the projects prioritized by the Government of Indonesia (GoI) in order to provide reliable mass transportation to and from Soekarno-Hatta International Airport. This research discusses electricity needs for the operation of Soekarno-Hatta Airport Railway and compared them to those of the existing substation. The availability of electric power became the most crucial aspect for the viability of the project and will depend on the capacity of substations that will sustain this train trip. It was assumed that Manggarai - Batu Ceper line will be integrated with other electric train service, which is Commuter Line, and this condition results in a clash as to their operation and electric power demand. Two separate services, two different companies, and two different types of train that use the same one line and substations are the focus of this research. This research examines the reliability of substations that already exist as well as the additional ones, if necessary. The findings of this research indicate that Karet and Manggarai substations require a slight additional capacity, but, overall, the existing substations remain reliable even though there will be an additional capacity in 2030 in order to maintain reliability in performing power supplies to two different services. It is calculated that the cost incurred if the capacity is added reaches USD 4.3 million. As for the cost of electricity, it is estimated that it ranges from USD 85,000 to USD 100,000/month for the first year with 89 trips per day.