This paper is devoted to the incorporation of the steady-state model of the unified power flow controller (UPFC) in power flow programs using a UPFC injection model. The adopted UPFC injection model is based on the representation of UPFC in steady-state conditions by two voltage sources in series with certain reactances. Using this UPFC power flow model, the effects of UPFC control variables on system voltage magnitude, line active and reactive power flow, total system losses, slack bus generated active and reactive power and the injected reactive power from voltage controlled buses are illustrated. Also, the effects of the UPFC location and the UPFC series converter coupling transformer reactance on power flows and on total system real power loss are studied. It is found that using this UPFC power flow model it is possible to show the power flow characteristics inside the UPFC converters, themselves.