An inter-spool energy transfer system is provided and includes a first spool, a second spool, which includes components that are rotatable at a different speed as compared to components of the first spool and an inter-spool interface system coupled to at least one of the components of the first spool and at least one of the components of the second spool. The inter-spool interface system includes a controller, which is configured to supply power to one of the first and second spools and to draw power from the other of the first and second spools.