Green Building Rating Systems (GBRSs) play a key role in assessing environmental impact and sustainability, and in facilitating decarbonisation in the building sector. Eight GBRSs were chosen for this comparative study: CGBL, BEAM Plus, BREEAM, Green Mark, Green Star, LEED, EDGE, and NABERS Energy. They are categorised into two main types: scoring-based rating systems and performance-based rating systems, based on their certification methodologies. Of these, BEAM Plus is a Hong Kong-based GBRS and the others are from other jurisdictions. This study compares the similarities and differences between the GBRSs, in particular taking a deep dive into energy-related requirements. The purpose is to gain insight into whether existing GBRSs sufficiently facilitate decarbonisation in the building sector.