One of the challenges of today is not only to find ways to produce green energy or building technologies to realize this but also to find methods for saving as much as possible the energy consumed. Today, the cost of consumed energy from computer systems occupies a considerable part of the total operating cost of a corporation. Consequently there is a need for finding and implementing techniques for saving consumed energy by these systems as much as possible. This paper will be shown the efficiency of Dynamic Voltage and Frequency Scaling (DVFS) and VM migration techniques for energy saving in a cloud data center.