Sandia National Laboratories (SNL) and National Renewable Energy Laboratory (NREL) have collaborated to develop the open-source Wave Energy Converter (WEC) modeling tool WEC-Sim, capable of running on a standard personal computer. Its main function is to simulate WECs of arbitrary geometry subject to operational waves; both regular and irregular waves. However, WEC-Sim Version 1.0 models a power take-off (PTO) as a simple linear damper. A collaborative effort between SNL and the Energy Systems group at Oregon State University (OSU) has resulted in the development of PTO-Sim, an additional WEC-Sim library for accurately modeling a WEC PTO system such as hydraulic or direct-drive. This development of PTO-Sim makes WEC-Sim a wave-to-wire model by adding functionality that extends WEC-Sim capabilities. The WEC PTO system is easily created with drag and drop PTO-Sim library blocks to build a model that can estimate absorbed and electrical power.