Upgrading a Feed-in Tariff (FiT) Solar System
If your system is still on the old Feed-in Tariff (FiT), the payments are valuable. Upgrades are often possible — but only if metering stays compliant and you notify your FiT licensee. Here is the cautious, step-by-step view.
The Feed-in Tariff scheme closed to new applicants in 2019. Existing accredited systems can still receive generation (and, where applicable, export) payments. A common myth is that any upgrade automatically voids FiT. That is not automatically true — but overconfident claims about 'getting paid twice' or skipping licensee checks are risky. Always confirm the metering plan with your FiT licensee before work starts. This page summarises the usual position under published Ofgem FiT guidance; a technically competent person should verify the detail against current Ofgem documents and your licensee's requirements for your site.
1. Can I replace my inverter and keep FiT?
Often yes — with notification
Replacing a failed or ageing inverter is generally treated as repair/maintenance of an accredited installation, not a new FiT application.
You should notify your FiT licensee of the change, keep capacity and accreditation details accurate, and ensure any new inverter and wiring stay within the scheme rules for your installation.
We can replace the inverter and help you gather the paperwork your licensee asks for. Do not assume silence is fine — tell them.
2. Can I add a battery to a FiT system?
Often yes — but metering must be right
Ofgem allows battery storage on FiT systems when your licensee is satisfied that electricity imported from the grid to charge the battery is not counted as solar generation.
AC-coupled batteries (separate battery inverter, usually after the generation meter) are commonly simpler. DC-coupled / hybrid setups often need a bi-directional or net generation meter so only genuine solar generation is recorded.
Ask your licensee for their battery/storage declaration or metering requirements before you order equipment. Self-use savings on your import bill are real; they are separate from FiT rules.
3. Can I add extra solar panels?
Possible — but FiT only pays on the original accredited capacity
Adding panels or increasing total installed capacity is a modification you must notify. Under current policy, extensions can keep accreditation for the original capacity; added capacity is not paid under FiT (export from extra capacity is typically via SEG or similar, not the old FiT export rate).
Do not add panels on the assumption that FiT payments simply scale up. Get licensee confirmation and a clear single-line diagram first.
4. What happens to generation payments?
Generation tariff usually continues on the accredited capacity
Generation payments are based on what your compliant generation meter records for the accredited installation, at your existing tariff, for the rest of the FiT term — provided scheme rules are met.
If the generation meter fails, is bypassed, or starts measuring non-solar energy (for example poorly integrated battery charge from the grid), payments can stop or be clawed back. Meter health checks matter.
5. What happens to export payments?
Check whether you are on deemed or metered export
Many older FiT contracts use deemed export (historically often 50% of generation) rather than a measured export meter. Others use metered export.
Adding a battery so you export less can reduce metered export payments. On deemed export, the deemed figure may continue — but switching meters, SEG, or licensee rule changes can alter that. Never plan on 'getting paid twice for the same energy' without written confirmation of your export arrangement.
Before a battery or hybrid inverter install, ask your licensee: am I on deemed or metered export, and what must change when storage is added?
Why old FiT systems still need a health check
FiT systems are typically 8–15 years old. Panels often outlast isolators, cabling terminations and generation meters. Brittle DC isolators and loose connections are fire risks; a failed generation meter stops payments. A health check before upgrades is sensible.
- DC isolators: Older rotary switches can become brittle.
- Cabling & MC4s: Loose or corroded connections can arc.
- Generation meter: If it fails or reads wrongly, FiT payments stop.
A sensible upgrade path (after licensee checks)
- Confirm with your FiT licensee: inverter swap, battery coupling method, and metering requirements in writing where possible.
- Inverter: replace a failed or inefficient string inverter with a suitable modern unit (hybrid only if metering for storage is agreed).
- Storage: add battery capacity using the coupling method your licensee accepts.
- Notify & record: send them the documents they request and keep copies with your FiT records.
Book a FiT Health Check
Ensure your system is safe and maximizing your returns.