In present scenario, the deregulated electricity market is well established in almost all the countries in the world. The main aim of this deregulated power system is to create the competition in electricity market and to reduce the customer prices. For that, the entire system has been unbundled into many sub companies to compete each other. The main key issues (technical challenges) of the deregulated power system are Transmission Cost Allocation (TCA), Transmission Loss Allocation (TLA), Ancillary Services Management (ASM), Available Transfer Capability (ATC) and System Reliability Management (SRM). It is necessary to monitor these key issues regularly for providing efficient power system with fair and transparent services to the consumers. This text book has covered the cost analysis on above key issues of the deregulated power system.