Some sub-Saharan African countries face the paradox of overcapacity in the power sector

where investments in electricity generation far exceed both demand and grid capacity

despite millions still lacking access to electricity. This imbalance stems from inadequate planning and external pressures from donors and private investors

who often prioritize generation over expanding transmission infrastructure. As a result

some power plants remain underutilized

placing financial burdens on governments and raising electricity costs for consumers. This study assessed overcapacity in Rwanda's power system using two key indicators: the plant utilization factor and reserve margin. We propose a coordinated generation and transmission expansion planning model to better align generation capacity with demand and grid development. The problem was analysed using PLEXOS software. Overcapacity in Rwanda rose from 29% in 2017 to 35% in 2023

as generation additions outpaced demand. However

with electricity consumption projected to grow by 10% annually

overcapacity could decline to 21% by 2028

based on committed and ongoing generation projects. Model results show that delaying selected generation projects and strengthening the transmission network could reduce overcapacity by 79% within 5 years and lower operating costs by 11.7% compared to the current master plan. These findings underscore the importance of integrated planning to improve system utilization and efficiency

offering a practical framework for other African countries facing similar challenges.