In this paper the authors present an evaluation of technical concerns that may arise from the deregulation of electric power systems, particularly including wheeling transactions. In the deregulation of the power industry, many independent power producers (IPPs) are seeking chances to be connected to the existing transmission systems under an open access environment. Some IPPs will sell power to existing utilities at a market price and others may participate in wheeling transactions with a third party, using the existing transmission system. This paper reports research about the impact of wheeling introduced in an existing electric power system. The evaluation of the impact on the existing utility power system is conducted by multiple perspectives such as: transmission loss, voltage profiles, and network congestion. Numerical analyses have been done on a standard IEEE power system. The optimal power flow was solved by varying the possible combinations of an IPP supplier and a customer load in wheeling transactions. The power output of the IPPs was assumed to be determined by an economic objective and therefore not controllable by the existing utility. The various numerical aspects were assessed based on the economic dispatch and AC load flow data.