For extensions, i.e. an increase in MEC at either an existing (connected) generator or planned (contracted) generator, you will need to complete section 3 of the NC5 / NC5A. Please provide the DG reference and Project Name of the original generator. Where is it an existing (connected) generator, please also provide the MPRN (Meter Point Registration Number).
Also, if know at the application stage, please advise if sub-metering is required for the extension. This can be provided in the cover letter accompanying your generator application