In recent years, load management (LM) programs are introduced as an impressive option in all energy policy decisions. Under deregulation, the scope of LM programs has considerably been expanded to include demand response programs (DRPs). Basically, DRPs are divided into two main categories namely, incentive-based programs (IBPs) and time-based rate (TBR) programs. In this paper, an economic model of responsive loads is derived based upon price elasticity of demand and customers' benefit function. In order to investigate the economic-driven and environmental-driven measures of demand response programs, a new linearized formulation of cost-emission based unit commitment problem associated with DRPs (UCDR) is presented. Here, UCDR is modeled as a mixed-integer programming (MIP) problem. The proposed model is applied to determine loads provided by DRPs and schedule commitment status of generating units. Moreover, the optimum value of incentive as a crucial issue for implementing DRPs is derived. Several analyses are conducted to investigate the impact of some important factors such as elasticity on the UCDR problem. The strategy success index (SSI) is employed to prioritize DRPs from the independent system operator (ISO) perspective. The conventional 10-unit test system is used to demonstrate effectiveness of the proposed methodology.