Building Integrated Photovoltaic (BIPV) microinverter system needs lower component counts and high efficiency at low power levels. In this context, this paper proposes a single‐phase Transformerless Single‐stage Buck‐Boost Microinverter with sensorless control for the Grid‐integrated BIPV system. The current estimation strategy is used to control the PV system, which reduces the costs and volume of the system. The leakage current of the system is reduced within the limits. It operates at a high level of efficiency, using an optimized number of active and passive components. In the absence of shoot‐through problems, reliability is high for the proposed topology. MATLAB/Simulink simulation with a laboratory experimental setup for the proposed inverter for the First Solar BIPV module is designed to validate the results. Finally, the proposed inverter was compared to different Buck‐Boost inverters at a power level of 70 W.