Abstract A general theory for the available work (exergy) carried by particle fluxes is developed ab initio by using a simple statistical thermodynamics approach. Relationships that may be used for both fermions and bosons are derived. The exergy flux of free particles involves an efficiency-like factor affecting the energy flux. This factor contains the environment temperature and the effective particle flux temperature and generally is different from the usual Carnot factor and the Landsberg–Petela–Press factor appearing in the exergy of blackbody radiation. Computations are performed for particular cases by using “exact” relationships and the classical (low speed) and ultra relativistic approximations. Both approximations show reasonable accuracy. Free Fermi particles carry less available work than Bose particles.