A common strategy for energy saving for wireless network devices is to stay in sleep mode for as long as possible when no data is being transmitted or received. The timings of packet transmission and reception are not determined only by the behavior at the physical and the data link layers; they strongly depend on the behavior of the transport-layer protocols used by upper-layer applications. For effective energy saving, therefore, it is important to understand the relationships between the behavior of the transport-layer protocols and energy efficiency. One effective method for lengthening the idle interval is by transmitting and receiving multiple packets in groups, which is called burst transmission. In this paper, we analyze the energy consumption of TCP data transfer with burst transmission over a wireless LAN. By comparing the energy consumption with and without burst transmission, we show that burst transmission can reduce the energy consumption in TCP data transfer by approximately 60 %. We also discuss which part of wireless LAN devices should be improved for effective energy saving.