This paper presents a design a 2.0kW solar photovoltaic (PV) system with a microcontroller-based power transfer switch designed for the intended 980W load of the third floor of the three-story building. The study determined that a 2.0 kW solar PV system can generate 8.92 kWh/day, enough for the 7.840kWh/day daily requirements based on the simulation using PVsyst. Four units of PV module were used for the design, with an individual 500W power rating. Four units of PV module were used for the design, with an individual 500W power rating. For the Microcontroller-Based Power Transfer Switch, an ACS712 current sensor was used to monitor current. The microcontroller was programmed to accept input from ACS712 and send a digital signal to the relay to change the power source. PVSYST simulates a generation of 3254 kWh/year. Interpreting the system output in kWh/day only the month of December was not able to reach the 7,840 Wh/day power demand while the rest other months averaging 8.92 kWh/day enough to energized 8 hours operation.