Legacy FIT repowering

Repowering a Feed-in Tariff (FIT) installation means repairing, replacing or increasing its generating equipment while preserving the accreditation attached to the original installation. The FIT scheme closed to new applications in 2019, but an accredited installation can continue receiving its generation payment, and any FIT export payment, for the rest of its eligibility period if it continues to comply with the rules.

The central point is that replacing equipment does not by itself cancel FIT accreditation. Ofgem’s December 2021 decision removed the old ambiguity, and its current generator guidance explains how repairs, replacement, capacity changes, batteries and metering are treated.

What can be replaced

For solar PV, Ofgem defines the panels and inverter as generating equipment. All or part of that equipment can be repaired or replaced while the installation remains accredited, provided that it:

remains at the accredited site
continues to use the same eligible technology
is not decommissioned
remains within the FIT scheme’s maximum capacity
continues to meet the metering and other scheme rules

There is no general Ofgem rule requiring the replacement panels or inverter to be the same make, model or wattage as the old equipment. A higher-capacity replacement is possible, but it becomes an extension and changes how eligible generation is calculated. The current Ofgem guidance also expressly allows replacement equipment that previously formed part of another FIT- or Renewables Obligation-accredited installation.

Temporary removal, for example while a roof is repaired, can be considered without ending accreditation. Permanently moving the installation to another property is different: FIT accreditation is tied to the original geographical site.

When the capacity changes

Total Installed Capacity (TIC) is the scheme quantity to establish before and after the work. If the TIC increases or decreases, the owner must tell the FIT licensee. An owner of a ROO-FIT installation must also update the installation’s accreditation record with Ofgem; most small domestic solar installations are MCS-FIT and are administered through their FIT licensee.

An increase using the same technology at the same site is an extension, whether it comes from extra equipment or more powerful replacement equipment. An extension commissioned on or after 15 January 2016 does not receive its own FIT generation or export support. The original installation keeps its eligibility date, tariff and eligibility period.

Where the original installation and unsupported extension share a generation meter, the reading is apportioned by capacity. For example, if a 4kW accredited installation becomes 5kW, 4/5, or 80%, of the shared generation reading is eligible for the original FIT generation rate. It is the ratio that matters; an example using a particular tariff rate or annual yield can create false precision.

If the TIC is reduced but remains above zero, Ofgem says the original eligibility date, tariff rate and eligibility period continue. The FIT licensee still needs the changed capacity so the central record and payment calculation are correct.

Adding more solar

Extra solar capacity at the same site normally forms an extension to the existing solar installation. It does not become eligible for a new FIT tariff. The practical metering and export choices depend on how it connects:

a shared generation meter can be apportioned by TIC where the scheme’s conditions allow
separately metered equipment can make the generation split clearer, but does not by itself create new FIT eligibility
if FIT-accredited and non-FIT capacity share the import or export metering, the owner can opt out of FIT export and seek a SEG tariff across the full TIC
receiving FIT export for one installation and SEG export for a genuinely different installation requires them to meet Ofgem’s strict separation conditions, including distinct import and export meters and different import and export MPANs

Those rules make “just add a second system” an unsafe general answer. The FIT licensee, SEG supplier, installer and DNO need to assess the proposed wiring and metering, not merely the position of the panels on the roof.

Adding a battery

Battery storage can be added without ending FIT accreditation, but the installation must still measure eligible renewable generation correctly. In particular, electricity imported from the grid must not be counted as FIT generation.

The labels AC-coupled and DC-coupled do not settle that question on their own. What matters is where the battery, inverters and meters sit, whether the battery can grid-charge and whether the FIT generation meter records only the permitted net renewable output.

Ofgem says the storage addition should be reported to the FIT licensee and, for a ROO-FIT installation, to Ofgem. The evidence includes an updated single-line or schematic diagram, details of the FIT readings and the storage equipment and commissioning date. An MCS-FIT owner adding storage should also submit the appropriate declaration from Ofgem’s co-location guidance.

Where a bi-directional generation meter is used, the licensee may need its make, model, operating information, metering certification, photographic evidence and confirmation of how it handles imports and exports. That is more than simply fitting a meter that happens to display two registers.

Ofgem recommends an MCS installer and the MCS battery standard for a storage system up to 50kW. It does not state that every FIT equipment replacement universally requires a new MCS certificate. The owner should establish the exact evidence required by the FIT licensee, the electrical work and any separate SEG application before commissioning it.

FIT generation and SEG export

FIT generation and SEG export can be received for the same accredited capacity. To do this, the owner must first opt out of the FIT export payment through the FIT licensee. FIT export and SEG export must not both be claimed for the same installation and capacity.

The decision is not freely reversible each month. After the first anniversary of FIT participation, Ofgem permits a change between opting in and opting out no more than once every 12 months.

Before switching, compare:

the installation’s own indexed FIT export rate
whether its FIT export is deemed or metered
the amount it actually exports after household use and battery charging
the current SEG rate and contract conditions

There is no timeless rule that SEG is better. Export tariffs change, FIT rates depend on the installation and deemed export can be valuable for a home that uses or stores most of its generation. Any current price comparison should be treated as a dated snapshot.

DNO and electrical approval

FIT accreditation and permission to operate in parallel with the distribution network are separate matters. A replacement inverter, added inverter or battery can change the generating capacity and protection arrangement seen by the DNO. The installer must review all existing and proposed generation and establish the applicable G98, G99 and, where relevant, G100 process before the system is connected.

Do not assume that retaining the old export limit or staying below 3.68kW of measured export preserves the old connection route. Registered Capacity and export are different, and the whole design must be assessed.

A safe repowering sequence

Find the FIT statement, accreditation details, original TIC, eligibility period, tariff and meter records.
Record the existing panels, inverter, generation meter, DNO approval and wiring before anything is removed.
Ask the FIT licensee in writing what it requires for the proposed repair, replacement, capacity change or battery.
Have a competent installer design the final system, metering and protection and confirm the DNO route.
Decide separately whether to retain FIT export or opt out and apply for SEG. Do not allow the payment periods to overlap.
Take dated meter readings at the point of any extension or reduction and retain photographs.
Keep the invoices, commissioning and electrical certificates, diagrams, equipment details, DNO correspondence and any MCS documents.
Notify the FIT licensee of the completed change and provide the evidence it requested. ROO-FIT owners must also update Ofgem’s register entry.

If a contractor says any replacement automatically ends FIT, that conflicts with Ofgem’s current guidance. If a contractor says any replacement is automatically safe, that is equally incomplete: capacity, site, metering, export and notification still have to comply.