The "Solar Doctor" Guide to Upgrading Your Feed-in Tariff System

Customer with a string inverter and an AC-coupled battery

If you were an early adopter of solar between April 2010 and March 2019, you are currently benefiting from the most generous green energy incentive in UK history. But as your original inverter approaches its 10th or 15th birthday, you might be facing a dilemma: Repair or Upgrade?

At Quantum, we are seeing a massive surge in "Solar Doctor" calls from homeowners in Bridgend and Cowbridge whose original inverters are failing. If this is you, don't just replace like-for-like. 2026 technology allows you to keep your payments and double your savings.

The 50% Assumption vs. The 20% Reality

When you joined the FiT scheme, smart meters didn't exist. The government simply assumed (deemed) that you exported 50% of your energy. You get paid for that 50% export whether you send it back or use it all yourself.

The catch? Without a battery, research shows most UK homes only actually use about 20-30% of their free solar energy. The rest is wasted. By adding a battery, you can use 100% of your power and still keep your full 50% "deemed" export payment.

The "Golden Rule" of FiT Upgrades

The #1 fear is losing the tariff. To stay 100% compliant with Ofgem rules, we follow the "No Improvement" rule:

• We cannot swap your old inverter for a "Hybrid" model. This is seen as "improving" the original system and can void your contract.

• The Solution: We install an AC Coupled Inverter. This sits next to your existing system. It captures the energy after it has been measured by your FiT meter but before it leaves your house, storing it safely in a battery for evening use.

  
  

Our 2026 Recommendation: SigenStor by Sigenergy

In light of recent industry shifts, we have moved our primary recommendation for FiT retrofits to SigenStor.

• Why SigenStor? It is an AI-powered, 5-in-1 system that acts as the perfect "bridge" for older systems.

• Smart Charging: It integrates with tariffs like Octopus Go. During the dark Welsh winters, it can charge itself from the grid at 7p/kWh at 2 AM, so you have cheap power ready for the morning—even if the sun isn't shining.

• Non-Grid Trading: While "Grid Trading" is a myth for FiT customers (you can't mix grid and solar energy), SigenStor focuses on "Self-Consumption," ensuring you never buy a unit of peak-price electricity again.

  
  

Book a "Solar Doctor" Health Check

Is your 10-year-old inverter clicking, flashing red, or underperforming? Don't risk your FiT payments with a "cowboy" fix. Let our MCS-accredited team assess your system, keep your contract safe, and show you how a SigenStor battery can make your original investment finally reach its full potential.