In this paper we study the energy cost (protocol processing and communication cost) and goodput of different flavors of TCP (Transmission Control Protocol) in ad hoc networks.We implemented a tes tbed and measured the actual energy cost as well as goodput of running TCP Reno, Newreno, SACK (Selective ACKnowledgement) and a version that combines Explicit Link Failure Noti_cation (ELFN)and Explicit Congestion Noti_cation (ECN) in Newreno. We see that the use of ECN & ELFN does yield higher good put in most cases with a corresponding lower total energy cost. We see an energy savings of between 20% and 500% depending on the network conditions.