The efficient utilization of solar energy is crucial for meeting the growing energy demands while reducing greenhouse gas emissions and dependence on fossil fuels. Solar panel tilt angle optimization plays a vital role in maximizing the energy output of photovoltaic (PV) systems. Determining the optimal tilt angle is essential as it directly affects the amount of sunlight captured by the solar panels. In the context of Indonesia, a country rich in solar resources and a rapidly expanding renewable energy sector, understanding the optimal tilt angle for solar panels is of paramount importance. This paper studies the optimal solar panel tilt angle calculation using Liu and Jordan Sky isotropic model-based approach. The numerical simulations were carried out for several main city locations of Indonesia. The objectives of the work are to address the suitable and optimal tilt angle of solar panels by proposing an approach based on the Liu and Jordan Sky Isotropic Model. The calculation result shows that the boundary for the tilted angle empirically satisfies all the mathematical domain of the inverse trigonometric functions. While, the optimal tilted angles will be differed for any location
