The user requirements and beam time scheduling of the Linac Coherent Light Source (LCLS) imposes a demand for fast changes in machine energy across the entire operating range of 3.3 - 15 GeV (480 - 10000 eV). Early operational experience during LCLS commissioning revealed this process to be problematic and error-prone, sometimes requiring substantial re-tuning at each change. To streamline the process, a software tool has been developed to gradually ramp the machine energy while the beam remains on, allowing beam-based feedbacks to continue to work during the energy change. The tool has considerably improved the speed and reliability of configuration changes, and also extends the capability of the LCLS, allowing for slow scans of the photon energy over a wide range. This paper presents the basic process, analysis of the performance gains, and possible future improvements. Show Partial Abstract