In principle the extension is treated as a new system and registered separately.
BUT the tariff will be based on the combined capacity of the original system plus the extension.
The existing FITs registration on the original system will be unaffected.
There used to be concessions for extensions within 12 months of the original installation, but these have effectively been rescinded.
See more here.
Yes. if you install systems of different technologies you will get the tariffs relevant for each (based on the capacity of each system).
If you install more than one system of the same type, the tariff level will depend on the combined capacity.
Yes geothermal heat is supported by the RHI (but geothermal power is not supported by the Feed-In Tariffs).
Chapter 4 of the government's RHI announcement says
Deep geothermal systems, sometimes also referred to as enhanced geothermal or hot dry rocks, will be eligible for the RHI. Deep geothermal will receive the same tariff as ground source heat pumps.
Geothermal systems tend to be relatively large and there are no MCS or equivalent standards so, for the RHI, Ofgem will verify eligibility based on the documentation required from RHI applicants as part of the accreditation process.
The Government has not yet finally decided how it will define 'capacity' - the parameter used to define where the tariff levels are set. Logically the so-called 'declared net capacity' (DNC) should be used to allow for variations between renewable energy types.
Yes, the Feed-In Tariffs only apply for systems up to 5 megawatts. That’s pretty big so will suit all household uses and most businesses, except for large factories.
Systems between 50kW and 5MW can alternatively choose to use the Renewables Obligations.
The tariffs apply to many types of renewable electricity, though not all. There is a full list of all types included on our page about eligible energy sources.