Retrofitting refers to the addition of new technology or features to older systems, for example :

• Power plant retrofit, improving power plant efficiency / increasing output / reducing emissions;
• Home energy retrofit, the improving of existing buildings with energy efficiency equipment;
• Seismic retrofit, the process of strengthening older buildings in order to make them earthquake-resistant;
• Naval vessels often undergo retrofitting in dry dock to incorporate new technologies, change their operational designation, or compensate for perceived weaknesses in their design or gun plan; and
• etc