Powering Tomorrow: A Deep Dive into New and Used Solar Panels

The sun, a colossal fusion reactor 93 million miles away, offers a boundless source of clean energy. Harnessing this power has become increasingly accessible and efficient, thanks to rapid advancements in solar photovoltaic (PV) technology. Whether you’re considering a brand-new installation or exploring the benefits of upgrading an existing system, understanding the nuances of new and used solar panels, their performance, costs, and upgrade potential is crucial.

The Evolution of Efficiency: From Watts to Yields

Solar panel technology has come a long way. What once required significant roof space for modest output now delivers impressive energy generation from a much smaller footprint. This improvement is largely down to increasing efficiency and panel wattage.

Technical Details: Size to Performance

The efficiency of a solar panel dictates how much of the sunlight hitting its surface is converted into electricity. Modern residential solar panels typically have efficiency ratings between 15% and 22%, with premium models exceeding 22% and even reaching upwards of 24-25% in 2025.

To put this into perspective, consider the typical dimensions of a residential solar panel: around 1.7 to 1.9 meters in length and 1 meter in width, equating to roughly 1.7 to 1.9 square meters per panel.

• Older Panels (e.g., 250W): A 250W panel from several years ago might have had an efficiency of around 15-16%. For a panel of similar dimensions, this would mean a lower power output per square meter.
• Newer Panels (e.g., 450W): Today’s high-efficiency panels, generating 400W to 450W (and even higher for commercial applications), achieve this with an efficiency of 20-22% or more within similar physical dimensions. This translates to a significantly higher power density.

Upgrading for Increased Yields: 250W to 450W in the Same Space

One of the most compelling reasons to consider upgrading older solar installations is the substantial increase in power output achievable within the same physical space. For instance, if you have an older system with 250W panels, replacing them with modern 450W panels can almost double your energy yield from the exact same roof area.

Let’s illustrate: Imagine a roof space that comfortably fits 10 solar panels.

• With 250W panels: Your total system size would be 10 panels×250W/panel=2.5kW.
• With 450W panels: From the same 10 panels, your total system size jumps to 10 panels×450W/panel=4.5kW.

This means you could generate nearly twice the electricity without needing to expand your solar array’s footprint, making it a highly efficient way to boost your home’s renewable energy production.

The Declining Cost of Solar: A Historical Perspective

The cost of solar panels has plummeted dramatically over the past decade, making solar energy more accessible than ever before. This decline is largely due to economies of scale in manufacturing, technological advancements, and increased global demand.

• Ten Years Ago (circa 2015): In 2015, the median installed price of residential solar panel systems in the US was around $5.06 per watt, which equates to approximately £3.74 per watt (using a conversion rate of 1=£0.74). While UK prices varied, the general trend was significantly higher than today.
• Six Years Ago (circa 2019): By 2019, global solar panel costs had fallen significantly, with some estimates putting the price per watt at around $0.40, or approximately £0.30 per watt. In the UK, median costs for 0-4kW systems were approximately £1,369 per kW.
• Today (2025): The cost of solar panels continues to fall. Current global prices are under $0.20 per watt, or approximately £0.15 per watt. In the UK, the average cost per kilowatt for a solar panel system has decreased by 4.5% between March 2024 and 2025. For a typical 4.5kW system for a 3-bedroom home, the estimated cost (including installation and battery) is around £5,800. This represents a significant reduction in real terms compared to previous years, making solar a truly competitive energy source.

Limitations of Upgrading with Feed-in Tariff (FiT) Installations

For many early adopters in the UK, the generous Feed-in Tariff (FiT) scheme (which closed to new applicants in March 2019) provided a strong financial incentive for installing solar panels. While the FiT offers attractive generation payments, upgrading your system can have implications.

Key Limitation: Under the FiT scheme, you generally cannot increase the total installed capacity (TIC) of your system and receive FiT payments for the additional generation. If you replace panels with higher wattage ones, your FiT generation payments are still typically based on the original accredited capacity of your installation. While you can replace faulty panels or perform like-for-like swaps without issue, significantly increasing your system’s output might not result in higher FiT payments for the additional generation.

It is crucial to notify your FiT licensee of any modifications that change your system’s TIC. While your generation tariff for the original capacity remains intact, any additional capacity installed after the FiT closure date is not eligible for FiT generation payments. However, you can still export any excess electricity from the upgraded system under the Smart Export Guarantee (SEG).

Expanding Your Solar Horizon: Secondary Solar Installations with Hybrid Inverters

If you’re looking to significantly increase your solar generation beyond the limits of your existing FiT accreditation, or if you simply want to maximise your energy independence, a secondary solar installation coupled with a hybrid inverter offers an excellent solution.

Hybrid Inverter Benefits: A hybrid inverter acts as the intelligent hub of your solar energy system, combining the functions of a traditional solar inverter and a battery inverter. This allows it to:

1. Optimise Energy Flow: It seamlessly manages the flow of electricity from your solar panels, to your home’s consumption, to battery storage, and to/from the national grid.
2. Integrate Battery Storage: Hybrid inverters are designed to work directly with solar batteries, allowing you to store excess solar energy generated during the day for use in the evenings or during periods of low sunlight. This significantly increases your self-consumption of solar power.
3. Facilitate Secondary Installations: For homes with existing solar arrays, a hybrid inverter can be crucial for integrating a secondary set of solar panels. This second array, often connected to the hybrid inverter and a battery, operates independently of your original FiT-accredited system.
4. Grid Independence and Backup Power: By storing energy, a hybrid system reduces your reliance on grid electricity, offering greater energy independence and often providing backup power during grid outages.
5. Smart Export Guarantee (SEG) Optimisation: While your original FiT installation might have deemed export payments, a hybrid system with a smart meter can accurately measure and optimise exports from your new panels and battery, potentially earning you more under the SEG.

How it Works with Secondary Solar: You could have your original FiT-accredited system continuing to operate as before, receiving its generation payments. Simultaneously, you could install an additional set of solar panels connected to a new hybrid inverter and a battery. The energy generated by this secondary array would power your home, charge the battery, and any excess could be exported to the grid under the SEG. This allows you to leverage the benefits of new, highly efficient panels and battery storage without affecting your existing FiT payments.

In conclusion, the solar energy landscape is continually evolving, offering homeowners unprecedented opportunities for clean energy generation and cost savings. While the decision to upgrade or install new panels involves technical and financial considerations, the long-term benefits of increased efficiency, lower energy bills, and reduced carbon footprint make it an increasingly attractive investment for the future.
For those with FIT systems which are grid tied, adding storage would make a difference to the cost of power from the grid. take note than you should use a export meter for the FIT system. The old way was to claim you use 50% of the production which is deceiving and in almost all case completely untrue. This could boost your FIT income to pay for additional upgrades and modernisation of your solar install.