Energy systems may be exposed to various uncertainties. In this chapter, in order to deal with severe uncertainty of upstream network price, robust optimization framework is presented to investigate uncertainty-based operation of multi-carrier energy system. Robust optimization technique determines the worst condition within the uncertainty and prepares appropriate strategies to handle such conditions in a way that safe operation of multi-carrier energy system is warrantied. So, a grid-connected multi-carrier energy system containing renewable and nonrenewable local generation units, combined heat and power (CHP), and boiler as well as electrical and thermal storage systems is studied under experiencing uncertainty of upstream network price, and the results declaring effectiveness of proposed technique are presented for comparison. It should be noted that simulations are carried out under general algebraic modeling system (GAMS) software.