Considerable work has been done to understand and improve the resilience of individual infrastructure components. However, systems of components, or even systems of systems, are far less well understood. Cascade effects, where the loss of one infrastructure affects others, is a major source of vulnerability which can lead to catastrophic disruptions of essential services. Interdependencies can also lead to large-scale failures when even a single component is disrupted and results in ‘cascading’ failures within and between networks. This is particularly true for power systems, as many other lifeline infrastructure systems rely on electricity. In this study we review the literature and give a primer on the vulnerabilities of networked energy infrastructure.