Although multiple-input multiple-output (MIMO) techniques provide attractive tools for reducing the energy consumption of wireless communications, many of them require transmitter-side channel state information (TCSI). While the effect of the TCSI on the MIMO channel capacity is well known, its impact on the achievable energy-efficiency is still not well determined. In this paper, we address this issue by studying the energy consumption of the singular value decomposition (SVD), beamforming, zero forcing and generalized Alamouti MIMO schemes. Although TCSI provides important savings in long-range communications, our results suggest that it is not critical when transmitting over short link distances. Results also show that large antenna arrays using schemes with a large diversity gain are energy-optimal for transmitting data over long transmission distances, while small arrays using schemes with a large multiplexing gain are more energy-efficient for performing short-range communications.