In the global mission to achieve a net-zero carbon footprint, the contribution of buildings is substantial, accounting for over one-third of the world's carbon footprint. To re-engineer the built environment in the direction of decarbonization, the building sector's operational energy needs our special imagination. The principal aim of the following research paper is to enhance building energy management by creating a digital platform that records design stage energy performance and benchmarks annual occupant consumption. The present study attempts to evaluate Kolkata’s residential high rises for their design stage energy consumption though whole building energy simulation by using design builder version 7.0.2.006. Envelope energy efficiency measures like wall, roof, and glass material changes show an annual energy performance improvement of 28.55% compared with a standard as built construction practice base case energy performance index value of 125.93 kWh/m2/year. The web-based energy profiling and benchmarking applications has been developed using Python’s Django framework. The website has been hosted on Python Anywhere. The portal features a home page, a page to add building details, and a personalised user dashboard with a building digital profile. The study shows that implementation of envelope interventions in the redesign have resulted in demonstrated improvements in annual energy performance. Integration with the web-based portal with initial design stage improvements serves to document and visualize tangible benefits in electricity bills and operational carbon emissions for the end-user, thus serving as the missing link of building operational energy performance.