The energy stored in big rotating turbogenerators of conventional power plants and some industrial motors, which gives them the urge to continue revolving, is referred to as inertia in the context of the grid. Since the grid frequency and the speed of rotating synchronous generators are magnetically locked, any sudden change in the grid frequency from its nominal or steady state value is resisted by the kinetic energy—or rotational energy—stored in the synchronous machines when the amount of power generated and the amount of demand differ. Additionally, the rate of change of frequency (RoCoF) will be arrested by inertia, giving power plants more time to adjust their supply to meet demand. Since the grid control systems can respond within the first few seconds, the inertia of conventional power plants contributes to grid stability. The main objective of the paper is to estimate the kinetic energy passing through inertia during arresting period corresponding to multiple grid imbalance events (generation loss event) that occurred throughout all of India’s five regional grid networks using PMU frequency data at the 1-second interval between December 2020 and December 2021 obtain from the North-Eastern Regional Load Dispatch Centre (NERLDC), Power System Operation Corporation Limited, Meghalaya (POSOCO), India. The secondary objective of the paper is to examine these generation loss grid events to determine the minimal inertial reserve needed for the grid to operate steadily as the amount of renewable energy sources grows. Furthermore, a few potential methods for producing actual inertia are discussed.