Internet Data Center (IDC) supports the reliable operations of many important online services. As the demand of Internet services and cloud computing keep increasing in recent years, the power usage associated with IDC operations had been surging significantly. Such mass power consumption has brought heavy burden on IDC operators. Recently there are extensive research on power management for IDCs. However, one important challenge faced by IDC operators has been overlooked. How to handle the uncertainties in IDC operations is a challenging task. The uncertainties come from both the dynamic workload and time-varying electricity prices. In this paper, we systematically investigate the problem of minimizing the operation risk of IDCs against those uncertainties at the same time guaranteeing quality of service under deregulated electricity market environment. We propose a novel hedging scheme and model the operation risk minimization problem as a bilevel programming. We also design an optimal hedging algorithm. We conduct extensive evaluations based on real-life workload data from Google and electricity price data from deregulated electricity market for multiple IDC locations. Results show that our scheme can significantly reduce the operation risk by countering the uncertainties.