Life Cycle Cost Perspective of Retrofitting the Istiqlal Mosque: Demonstrating Long-Term Savings of Green Public Buildings

Retrofitting projects for public buildings are often perceived as costly, reinforcing the misconception that green buildings impose high financial burdens. This paper develops the analysis of the Istiqlal Mosque retrofit, a case previously studied from the perspective of retrofit costs and Energy Use Intensity (EUI), by applying a life cycle cost (LCC) framework. The renovation, with a total investment of IDR 511 billion, reduced EUI by 23.81% and electricity expenditure by approximately IDR 718 million annually. By separating capital costs between energy-related and non-energy interventions, and by considering a 20-year horizon of electricity and maintenance savings, the LCC analysis reveals that operational savings systematically lower the total cost of ownership. The study establishes a benchmark of IDR 247,472 per square meter per 1% reduction in EUI, providing a practical budgeting reference for large-scale retrofits in tropical public buildings. These findings demonstrate that the longer a green building operates post-retrofit, the lower its effective annual cost becomes, thereby challenging the notion that green buildings are inherently expensive.