SmartGridToolbox is an open source simulation framework for studying smart grids and future electricity grids. It consists mainly of a C++ library that allows researchers to simulate power flows, multiple kinds of consumer loads, renewable and other generation and optimised control mechanisms. It features a high degree of flexibility and extensibility, the ability to interface with other tools, a component library, and various power flow solvers. It emphasises future and smart grids and optimised control. It is closely coupled with PowerTools, ORG’s library for modelling and solving optimisation problems for electricity grids.