Data-driven key performance indicators and datasets for building energy flexibility: A review and perspectives

•Studies on data-driven methods for building energy flexibility quantification have been reviewed.•Existing data-driven energy flexibility KPIs have been systematically categorized.•Various aspects of the KPIs, including application, stakeholder, complexity, data requirements, and popularity, have been analyzed.•Public datasets for energy flexibility studies have been reviewed and summarized in a standardized data collection process.•Research trends, open questions, and future opportunities are identified.