It all comes down to the acceptable definition of a 'site'. One site can only have one PV system, and any multiples of panels/inverters will be added together to get the TIC that determines the tariff.
This is OFGEM's most recent guidance on this:
Defining "Site"
2.4. "Site" is defined as:
"the premises to which are attached one or more accredited FIT installations or eligible installations in close geographical proximity to each other, to be determined as required by the Authority by reference to: The relevant Meter Point Administration Number (MPAN) for electricity supply Street address OS grid reference
and any other factors which the authority at its discretion views as relevant."
2.5. In addition to the requirements set out in the definition of "site", the other factors that we will also assess the installation against include the requirements of the RO Order and our definition of "generating station".
2.6. A domestic or non domestic postal address at which an installation (or several installations of the same technology) is located would normally be viewed as a single site, but not in every case. Applications are assessed on a case-by-case basis taking into account each of the factors detailed in paragraphs 2.4 and 2.5 above. The overall bounds of an installation are taken into account when making a determination.
2.7. In areas where no postal address exists, the Ordnance Survey (OS) grid reference will be taken from the position of the import/export meter(s) and the area served by the meters will normally be viewed as a single site.
2.8. For installations located on a private wire network, the point where the private wire network connects to the grid will be considered the import/export point of the site. All installations located on a private wire will be considered to be located on the same site. Only electricity which enters the national grid system is eligible to receive FITs export payments.
