An essential problem in a deregulated power system is the long-term availability of peaking capacity. One potential solution, which has received increasing attention, is the demand reduction/exchange program in power markets. A voluntary real-time demand reduction program provides an opportunity for customers to reduce their demands during times of high prices and share the benefits of the program. An Independent System Operator (ISO) can use a fixed price to buy demand reductions from customers; the benefits obtainable, due to the relief of line congestion constraints and market power, can be shared both by the ISO and program participants. If the optimal curtailment price bid can be determined then social welfare can be maximized. For these purposes, the basic task is to determine a rate structure, which gives incentives to both the ISO and the customers. The structure should minimize the cost of generation and maximize the economic benefit to the customers. In this paper, two solution formulations, including various levels of network constraints, are proposed to obtain the optimal curtailment bid and the economic impacts of the programs. Test examples are used to demonstrate the potential benefits obtainable for the ISO and participants from the voluntary demand-reduction programs.