The electricity grid faces challenges such as rising electricity demand and the integration of solar panels, wind turbines, electric vehicles (EVs), heat pumps, etc. Moreover, smart technologies are being added, providing a wealth of data. The industries associated with these challenges must perform complex calculations to assess the present and future state of the grid. The vast scale and diverse applications demand faster calculations that are cross-platform compatible. Power Grid Model is an open-source library with a C++ core and a well-defined Python API. It conducts state estimation, power flow, and short-circuit calculations for symmetric/asymmetric grids. The library is actively employed in 10+ applications within Alliander. Other major grid operators in the Netherlands, as well as researchers and stakeholders throughout the grid technology chain, use the library to conduct academic, technical, and feasibility studies. In this presentation, we will explore the power-grid-model library, its capabilities, active and future use cases.