The Feed in Tariff encouraged hundreds of thousands of UK homeowners to install solar panels between 2010 and 2019. Many of these systems are still running today and earning very generous FiT rates. Because the incentives were so strong, the most common questions we hear are:
• Can I add more solar panels to my FiT solar system?
• Can I add battery storage to a FiT system?
• How do I upgrade my feed in tariff solar panels without losing my contract?
So, can you upgrade your FiT system? The good news is that yes, you can upgrade a FiT system. You can replace panels, add additional panels, and add battery storage, as long as the upgrade is done correctly and the original FiT paperwork remains compliant.
Case Study: A Complete FiT Upgrade with New Panels and a Tesla Powerwall 3
In 2011 we installed a 19 panel solar PV system for a homeowner under the Feed in Tariff scheme. Fifteen years on, the panels were still generating close to 3,000 kWh per year and the original inverter was still operating, but the homeowners wanted higher output and the benefits of battery storage. Just recently they upgraded the system with 20 modern 500 W panels and a Tesla Powerwall 3 while keeping their existing Feed in Tariff contract exactly as it was. This case study shows how a FiT system can be upgraded safely, what rules must be followed to protect the tariff, and how adding new solar capacity and a battery can significantly increase annual savings.
See our video for more details:
Can I Add More Solar Panels to My FiT Solar System?
You can upgrade your feed in tariff solar panels as long as the original FiT-registered inverter stays within its original rated output. The FiT scheme only covers the array listed on your original commissioning documents. You can add additional panels, but they cannot feed into the FiT inverter. Instead, they must be wired into a new inverter or a hybrid battery system.
In the case study property, the old 185 W panels were removed and replaced with modern 500 W bifacial panels. In this installation:
• 7 new panels feed the original FiT inverter
• 13 additional panels feed the new Tesla Powerwall 3
This kept the inverter rating unchanged and protected the FiT contract.
Can I Add Battery Storage to My FiT System?
Yes. Adding battery storage to solar panels is allowed under the Feed in Tariff. And it is probably one of the most effective ways to elevate your FIT system. Here's why:
• A battery can store excess FiT solar
• A battery can charge from the grid
• A battery can support a second solar array
• None of this affects your FiT payments
Best Tip for FiT Owners: Replace FiT Export with a Modern Export Tariff
FiT generation payments are excellent. FiT export payments are not. FiT export pays about 5p per kWh. Modern export tariffs pay far more:
• Octopus Go Export about 15p
• Octopus Flux up to 29p at peak times
• E.On export around 15p
You can opt out of FiT export while keeping FiT generation. This is exactly what the homeowner will be doing after the upgrade. This is one of the easiest ways to increase income from a FiT system.
How to Upgrade My Feed in Tariff Solar Panels Safely
To sum up, in order to upgrade without losing the contract, you must follow these key rules:
1. Keep the original FiT inverter rating the same
You can replace it if it fails, but the replacement cannot exceed the original output rating.
2. Keep the FiT generation meter readings consistent
The meter must continue to measure only the FiT system generation.
3. Separate the FiT array from any new solar panels
Any new capacity must run through a new inverter or a battery system like Powerwall 3.
4. Document the upgrade clearly
Your installer must record which panels belong to the FiT system and which belong to the new system.
5. Do not alter the declared net capacity on your FiT paperwork
Only the original system is eligible for the tariff.
What are the benefits of upgrading your FiT solar system?
Upgrading a Feed in Tariff solar system is entirely possible and often highly beneficial. You can replace old panels, add new capacity, install battery storage, and keep every penny of your FiT generation rate as long as the system is configured correctly.
The case study shows that combining a FiT system with a modern solar and battery installation delivers high earnings, strong bill savings, and full energy resilience.
If you would like Spirit Energy to assess your own FiT upgrade options, we are happy to help.
