Do we need to separately meter our onsite renewable energy system? If so, do the meters need to meet the advanced metering requirements?

Yes, and yes.

When identifying all of the energy sources that serve your building, you must include both renewable and nonrenewable sources. Renewable sources include wind turbines, photovoltaic panels, solar thermal panels, and geothermal. If any of these energy sources serve your project, they must be metered separately at the building level.

Remember that metering for onsite renewable energy is unique to EAc5; it is not required under the related building-level energy metering prerequisite (EAp3). All meters that are used to comply with EAc5—even building-level renewable energy meters—must meet the advanced metering requirements outlined in the credit.