  Understanding the physics of non-equilibrium systems remains as one of the
major open questions in statistical physics. This problem can be partially
handled by investigating macroscopic fluctuations of key magnitudes that
characterise the non-equilibrium behaviour of the system of interest; their
statistics, associated structures and microscopic origin. During the last
years, some new general and powerful methods have appeared to delve into
fluctuating behaviour that have drastically changed the way to address this
problem in the realm of diffusive systems: macroscopic fluctuation theory (MFT)
and a set of advanced computational techniques that make it possible to measure
the probability of rare events. Notwithstanding, a satisfactory theory is still
lacking in a particular case of intrinsically non-equilibrium systems, namely
those in which energy is not conserved but dissipated continuously in the bulk
of the system (e.g. granular media). In this work, we put forward the
dissipated energy as a relevant quantity in this case and analyse in a
pedagogical way its fluctuations, by making use of a suitable generalisation of
macroscopic fluctuation theory to driven dissipative media.
