With the increase of computing capacity of big data centers (or we say cloud), energy management is becoming more and more important. In this chapter, we will introduce the latest development of research on the energy management of green cloud data centers. First, we will introduce power metering methods for data centers, including both server power metering and virtual machine (VM) power metering. For physical server, its energy can be measured using power distribution unit, so we mainly focus on VM power metering. Second, we will discuss how to leverage the intermittent renewable energy to reduce total carbon emissions for the geographically distributed data centers.We consider using energy storage devices (ESDs) to store renewable energy and the brown energy when its price is low, so as to reduce carbon emissions within the budget of energy cost. We also discuss how to deploy ESDs, wind turbines, and solar panels for each data center to take the advantages of energy sources in different locations. Finally, we consider selling energy back to the power grid, so that the energy cost can be greatly reduced while retaining a lower level of carbon emissions.