On behalf of all members of the steering, organizing, and technical program committees of SEST 2020, we are pleased to invite our fellow colleagues to join us in the third edition of the SEST conference series which will be held in Istanbul, Turkey, from 7-9 September 2020. Governments around the world are investing heavily in smart energy systems and technologies (SEST) to ensure optimum energy use and supply, enable better planning for outage responses and recovery, facilitating the integration of heterogeneous technologies such as renewable energy systems, electrical vehicle networks, and smart homes around the grid. Smart energy systems present enormous engineering challenges in the design and integration of energy and electrical grids with communication and network technologies, along with substantial questions of security and privacy of different components within the grid. The SEST conference aims at providing an opportunity to discuss various engineering challenges of smart energy system design and operation by focusing on advanced methods and practices for designing different components and their integration within the grid. It also provides a forum for researchers from academia and professionals from industry, as well as government regulators to tackle these challenges, and discuss and exchange knowledge and best practices about design and implementation of smart energy systems.