A generating set (8502) is a combined unit in which a prime mover — diesel engine, gasoline engine, wind turbine, etc. — is permanently or functionally coupled with an alternator or generator. A standalone alternator or generator presented without its prime mover is classified under 8501. If the prime mover and generator are imported together as a functional unit, 8502 applies.

Fuel-cell and other non-wind, non-reciprocating-engine sets fall under 850239 ('other generating sets'). Hybrid units that combine, for example, a diesel engine with a battery buffer are assessed based on the principal source of motive power; a binding ruling is advisable for novel configurations not clearly described by the existing subheadings.