We consider an Energy Packet Network (EPN) model where the service times of the packets follow a Coxian distribution. EPNs are a recent type of models proposed by Gelenbe and his colleagues to study the interactions between energy consumption and the processing or the transmission of data. We prove that such a network has a product form solution for its steady-state distribution. We also state some sufficient conditions for the existence of the flow equations. Finally we study the performances and the energy consumption and we show how to optimize the assignemenl of Δ solar panels over a sensor network.