The importance of deploying energy efficient networks has vastly increased due to the rapidly growing nature of power consumption of ICT industry. This requires redesign of networks or modification to existing networks that could prove to be energy efficient. In this paper, two telephone networks namely traditional Public-Switched Telephone Network (PSTN) and Voice over Internet Protocol (VoIP), are extensively examined in terms of energy consumption by means of measurements on our University Campus systems, modeling and actual experiments. Results show that the VoIP system is more energy hungry with respect to traditional PSTN. We then devise possible solutions which are more efficient in terms of energy than current technology.