Energy correlations are universal QFT observables that characterize angle distribution of energy in a given state. They are used to describe hadronic events at colliders. We review their definition, properties and computations in conformal field theories (CFTs). In CFTs energy correlations are examples of correlation functions of the so-called light-ray operators (more precisely the ANEC operators). We describe OPE for light-ray operators and use it to make new predictions for energy correlations in N=4 SYM and the 3d Ising model.