In this paper, we consider energy cooperation in a smart grid scenario. We assume that grid nodes act as prosumers, who can generate energy thanks to harvesting procedures, and exploit the presence of a smart grid gateway that enables energy and money transactions between local and external prosumers. We propose to adopt a game theoretic approach, where the prosumers participating in the smart grid can efficiently improve their revenue. We built a simulator, in which we can tune the smart grid price settings, and compared the game theoretic approach with "always sell" , "always buy," and "random" strategies through smart grid simulations with 500 participants.