In this work, a reactive power-voltage (QV)-based framework to evaluate the voltage instability sensitivities of power system buses to increase in renewable energy (RE) penetration has been developed using two sensitivity indices, namely, Critical Voltage Sensitivity Index (CVSI) and Critical Reactive Power Sensitivity Index (CQSI). The rise or fall in the critical voltage level is measured by CVSI and the reactive power loss intolerance of each bus is evaluated by the CQSI as the RE penetration level increases. The bus sensitivity analysis obtained from the CVSI and CQSI provides information on the voltage instability sensitivity of each power system bus to increase in RE penetration level. The proposed methodology has been evaluated using IEEE 14-bus system and New England 39-bus system. DIgSILENT PowerFactory was used to perform the simulations and Matrix Laboratory (MATLAB) used to analyse the results. The sensitivity analysis of the buses can provide insights on the most suitable placement for large reactive loads or devices such as Flexible Alternating Current Transmission Systems (FACTS) as the RE penetration level (PL) increases.