The Screening Tool for Energy Evaluation of Projects (STEEP) is designed to help improve energy use efficiency in water and wastewater treatment systems. This publication provides a detailed overview of STEEP and guides users on how to apply it during energy use assessments of proposed or existing water supply and wastewater systems. Since 2017, STEEP has been under continuous development based on pilot assessments carried out in various projects financed by the Asian Development Bank. STEEP is available online and can be downloaded for free.