Buildings play a central role in the clean energy transition, which is why it is vital to understand how energy is consumed in this sector. Energy performance certificate databases are considered a key source of information on the characteristics of built building stock. Despite a growing portfolio of studies based on information from such databases, little is known about energy consumption in offices. This paper explores the modelled energy performance of existing offices in Spain, using data from 13,701 energy performance certificates collected by the Catalan Institute of Energy (ICAEN) in 2013–2018. Offices were found to consume between 202.66 and 212.10 kWhp/m2·year and were mostly ranked in classes C and D (~64%). Offices with E, F or G labels represent ~28% of the sample while A and B energy ratings are very scarce (~8%). Key drivers of energy consumption variation were found to be the office type, construction period, climate zone, renewable energy use, energy certification procedure and motivation for obtaining an energy performance certificate. Ownership was not found to affect average calculated energy consumption. The results will help policy makers to plan future energy conservation strategies.