Buildings contribute to one-third of the total energy usage in India with the commercial buildings forming about 1/4th. Given the net zero targets, there is a need to make both the existing and new commercial buildings energy efficient by adopting green building practices. But there are only a few performance-based studies in the Indian context that quantify the operational energy savings of existing green commercial buildings. This study investigates the operational energy performance of commercial buildings certified with the Indian Green Building Council (IGBC) Commercial Existing Buildings (EB) Operations & Maintenance (O&M) rating system. The scope is limited to 38 buildings that operate day & night - 24X7 (BPO type buildings) and obtained certification during 2022 - 2024. The actual energy usage with respect to Energy Performance Index (EPI in kWh/m2/year) and the Average Annual hourly Energy Performance Index (AAhEPI in Wh/m2/hour) based on a weighted average approach was analyzed at an overall level and were also normalized with respect to green certification level, built-up area and the climatic zone. At an overall scale, there is a positive correlation observed between the EPI and AAhEPI, with the buildings exhibiting an average EPI of 163.5 kWh/m2/year, AAhEPI of 20.8 Wh/m2/hour and an energy savings of 52.6% compared to the existing baseline. Buildings with higher level of certification have exhibited lower EPI and AAhEPI with narrower confidence interval ranges across buildings with larger built-up area, higher levels of certification and those located in the temperate zone. This study can help in understanding the effect of climatic zone, varying operational hours and building scale variation on EPI and AAhEPI values to develop context specific benchmarks for energy efficient buildings and promote the awareness of green certification in enhancing the energy performance of existing commercial buildings in India.