The United Nations Development Program reported that two-thirds of the world's population will be living in cities by 2050, which would account for more than 60% of the world's energy consumption. Developing countries experience substantial urbanization and informal settlements compared with other parts of the world. This indicates a paradigm shift in the global energy landscape, which heralds an increase in greenhouse gas emissions. According to Indonesia's National Energy General Plan (PR 22), solar panels are expected to cover at least 25% of rooftops. In Uganda, the Sustainable Energy for All (SE4All) program aims to ensure high penetration of solar energy in the country. This study aims to integrate clean energy into low-cost housing development for sustainable cities in Uganda and Indonesia. We propose an optimal energy system and examine the most significant design parameters that exhibit a desirable performance ratio and energy yield. This project was undertaken in two stages: energy yield estimation and detailed energy system design using two different software programs. Stage 1 aimed to estimate the energy yield based on the available roof area considering existing homes in Uganda and Indonesia. A photovoltaic (PV) array was designed with suitable inverters, tilt angles, and orientations. Stage 2 was intended to determine the optimal tilt angles. Five different PV systems were developed and tested using the optimal tilt angle determined earlier. Finally, an optimizer was integrated into the PV system to investigate potential improvements in the energy yield. The inclusion of an optimizer significantly increased the energy yield from 0.5% to 5.3%. For Uganda, the levelized cost of electricity (LCOE) with and without an optimizer ranged