  Thermal machines perform useful tasks--such as producing work, cooling, or
heating--by exchanging energy, and possibly additional conserved quantities
such as particles, with reservoirs. Here we consider thermal machines that
perform more than one useful task simultaneously, terming these "hybrid thermal
machines". We outline their restrictions imposed by the laws of thermodynamics
and we quantify their performance in terms of efficiencies. To illustrate their
full potential, reservoirs that feature multiple conserved quantities,
described by generalized Gibbs ensembles, are considered. A minimal model for a
hybrid thermal machine is introduced, featuring three reservoirs and two
conserved quantities, e.g., energy and particle number. This model can be
readily implemented in a thermoelectric setup based on quantum dots, and hybrid
regimes are accessible considering realistic parameters.
