Today's US power markets offer new opportunities for the energy consumers to reduce their energy costs by first promising an average consumption rate for the next hour and then by following a regulation signal broadcast by the independent system operators (ISOs), who need to match supply and demand in real time in presence of volatile and intermittent renewable energy generation. This talk proposes a management framework for the data centers to participate in the power markets. First, I will discuss how to solve the data center "regulation service (RS)" optimization problem to determine the optimal average power consumption and regulation quantity that minimize the energy cost. I will then discuss dynamic "power capping" policies to modulate the real-time power consumption in response to ISO requests while maintaining the desired quality-of-service (QoS). Experiments on real-life servers indicate that data center power regulation can achieve dramatic energy cost reductions.