Within and between the electricity, fuels, transportation, buildings, and manufacturing sectors, increasing interconnectedness and complexity are creating opportunities and challenges that can be approached from a systems perspective.  Some of the most transformational opportunities exist at the systems level.  They are enabled by the ability to understand, predict, and control very large scale and interconnected complex systems.  Systems solutions can be broadly impactful across multiple technologies and sectors.

This chapter presents a holistic view of the energy system and explores the opportunities in energy systems research.  Systems approaches can help to identify critical technology needs and can also be used to develop solutions to complex energy challenges.