In this paper, we present the results of a detailed measurement study of the computational energy cost of different TCP variants when used in mobile ad hoc networks. The studied TCP variants are TCP New-Reno, Vegas, SACK, and Westwood. We used a hybrid approach using simulation and emulation, through SEDLANE emulation tool. This study investigates different packet loss models (congestion, link loss, signal loss, interference) with different ad hoc routing protocols (reactive and proactive). The study demonstrates that the fast retransmit/fast recovery phase has a mush lower energy cost than both slow start and congestion avoidance phases, sending more TCP data bytes in a shorter period of time.