Cybertronians use Energon as an energy storage medium.
Energon is stored in dedicated Storage Units, Energon Rods (25 ergons), or Energon Cubes (100 ergons).
Both rods and cubes can be compressed into concentrated energon, they take up 1/5th the space, but are more volatile than uncompressed energon.

Cybertronians who run out of energon become depleted.

See also: Energon Cost and Energon Reserve