In battery powered systems such as wireless sensor networks, energy eficiency is one of the most important system design goals. In this paper, energy eficiency is examined from the perspective of data consistency, which includes both temporal consistency and numerical consistency, and considers the application specific requirements of the data and data dynamics in the data field. We jrst formally dejne the energy-eficiency problem with the goal of delivering a minimum number of messages under the constraint of data consistency. Then, we give the formal dejnition of the data consistency. To achieve both consistency and energy e@ciency, we propose a data collection protocol named Alep, which adapts the data sampling rate to the data dynamics in the datajeld and keeps lazy when the data consistency is maintained. From the results of a comprehensive sirnulation we jnd that the proposed approach indeed reduces the number of delivered messages by more than 20%, and improves the accuracy of the sampled data.