Simulating cyber-physical energy systems such as data centers requires the characterization of the energy interactions between the computing units and the physical environment. Such interactions involve discrete events such as changes in operating modes of cooling units, and also transient processes such as heat flow. An event-based simulator fails to capture continuous transient effects while a time-stepped simulation can ignore events occurring within the decision interval. This paper proposes an error-bound hybrid simulator that integrates discrete event-driven (ED) simulation and finite-horizon time based simulation (FHT) and simulates energy interactions in a cyber-physical energy system. We apply this simulator to a data center case and validate the simulation results by comparing them with simulations performed in previous literature. We also evaluate the accuracy of the simulator by comparing the test case results with realistic data obtained from a real data center deployment. The error bound of the simulator is a user input and influences the time interval of the ED and FHT modules.