With growing great interest in the energy problems, real-time pricing (RTP) for power systems has attracted attention in the world. In our research, a new distributed optimization method is proposed for RTP. It is based on negotiations between players (consumers, suppliers and distributors) through information networks. Then we developed a graphical and scalable multi-agent simulator for RTP which is named “RTPsim” for further investigations. RTPsim enables us to conduct numerical simulations in various conditions and various scales. This paper shows the new distributed optimization method based on negotiations, the features of our graphical and scalable RTP simulator and examples of simulation results.