The need for a more environmentally friendly aircraft is driving the designer towards the aircraft electrification. In particular, new aircraft concepts with hybrid-electric and full electric propulsion system are currently proposed. The propulsion system electrification also entails novel requirements for the aircraft on-board systems. The present work is focused on the definition of an electrified on-board system architecture to be integrated with hybrid-electric or full electric aircraft. A small propeller driven regional aircraft is considered as reference for this study. Electrified environmental control system, ice protection system, actuation system are analyzed and preliminary designed. This has driven the electric system definition and sizing also considering possible synergies with the electrified propulsion system. Finally, the systems masses and their power requirements are analyzed together with new possible enhancements.