As Australia’s solar fleet matures, many older systems installed 15–20 years ago are showing signs of decline — panel degradation, inverter failure, and reduced energy yield. In response, asset owners are increasingly turning to repowering solar PV systems: the process of replacing or upgrading aging solar infrastructure to improve performance, ensure compliance with updated standards, and extend system life.

Repowering can deliver significant long-term benefits, but it also involves technical, financial, and regulatory considerations. Knowing when to repower, what to replace, and what can be reused is essential to making a sound investment.

Need help assessing whether your system is due for repowering? Contact GSES at info@gses.com.au for expert system audits, compliance reviews, and design support.

Understanding PV System End-of-Life

There is no single “expiry date” for a solar PV system, but there are several indicators that suggest it may be nearing the end of its effective life:

• Performance degradation: System peak output may drop below 80% of its original peak output.
• Inverter failure: Most string inverters last 8–12 years, and replacements for older models are often unavailable.
• Increased Fault Rate: As systems age, it is possible that the rate at which faults appear can increase, this is due to increased component failure due to exposure to the elements.
• Component corrosion or wear: Mounting hardware, DC isolators, or cabling may be weathered or non-compliant.

While a system may still be generating, its underperformance, non-compliance, or reliability risk may justify replacement.

Examples of critical faults that may justify repowering

From left to right:

1. Severely burnt PV module showing hotspot and cell degradation.
2. Melted backsheet and scorched cabling under the array—signs of thermal damage and potential fire risk.
3. DC isolator fire damage due to component failure or poor installation—non-compliant and hazardous.

When Does Repowering Make Financial Sense?

Repowering a solar PV system represents a significant capital investment, so it’s critical to assess whether it makes financial sense through a detailed and structured cash flow analysis. This analysis should compare the lifecycle performance and costs of maintaining or partially repairing the existing system against fully or partially replacing it.

The first step in this process is to assess the projected energy output under each scenario. This includes measuring the current system’s performance in terms of kilowatt-hours per kilowatt-peak (kWh/kWp/year), taking into account degradation and system faults. That figure should then be compared to the estimated output of a newly repowered system using modern, high-efficiency modules and inverters. Improved energy yield from repowering may result not only from better module efficiency but also from enhanced inverter performance, improved MPPT matching, and reduced downtime.

Revenue modelling is another key component of the analysis. The financial return from a PV system depends heavily on the tariff structure. When modelling revenue over a 15-20 year period, it’s also important to include reasonable assumptions for energy price escalation, load profile changes, or future policy shifts that could affect system value.

A comprehensive cost breakdown is essential to understanding the true impact of each scenario. Capital expenditure for repowering will include the cost of new modules, inverters, balance-of-system components, and labour. Additionally, the analysis must account for the cost of removing and disposing of legacy equipment — an often-overlooked expense that can make full system replacement more costly than a new “greenfield” installation. For example, dismantling aged and possibly corroded components, disposing of panels with outdated certifications, and reworking cable runs can be labour-intensive and expensive. Repowering, where feasible, can reduce some of these costs by allowing selective reuse of compliant infrastructure such as mounting rails, cable trays, or switchboards, provided they meet current standards and have remaining service life.

Operational costs before and after repowering should also be compared. Legacy systems often require more frequent maintenance and have higher failure rates, especially as inverters approach end-of-life. A repowered system with modern equipment may reduce ongoing O&M costs significantly, while also benefiting from new warranties and monitoring capabilities. It’s also important to consider lost revenue during the replacement process — particularly if the site will be offline for several weeks or months — and factor this into the total cost of the repowering project.

Once the performance and cost inputs are established, a cash flow analysis should be done with the legacy system and the repowered system side by side.  This analysis will determine key investment metrics such as Net Present Value (NPV), Internal Rate of Return (IRR), Levelised Cost of Energy (LCOE) and payback period. These metrics allow stakeholders to quantify whether the repowered system delivers a better financial outcome than maintaining the status quo or undertaking a full system rebuild. A positive NPV, a healthy IRR, and an improved LCOE aligned with internal investment thresholds can justify the repowering effort.

What Can You Reuse? A Practical Guide

Despite its benefits, repowering is not always straightforward. Compatibility issues can limit what equipment can be reused. For instance, older solar modules were typically 50mm thick, whereas most modern modules are between 30–35mm. This difference means that while mounting rails might theoretically be retained, the mid and end clamps will almost always need to be replaced. Similarly, even if cabling appears intact, changes in AS/NZS 5033 and AS/NZS 3000 may render older wiring, conduit, or DC isolators non-compliant. Inverters may also need to be updated to meet current grid support and DNSP requirements, particularly under AS/NZS 4777.2. Consequently, even partial reuse of infrastructure must be assessed against current technical and regulatory standards.

Ultimately, repowering makes financial sense when the improved energy yield, enhanced compliance, and reduced maintenance burden of a new system outweigh the capital and removal costs required to get there. If a significant portion of the infrastructure can be retained — without compromising compliance or performance — repowering can be a highly cost-effective way to extend the system’s life by another 15 to 20 years. However, if too many components must be replaced or brought up to code, a full replacement may be more appropriate. A carefully constructed cash flow model, grounded in accurate technical and economic assumptions, is the most reliable way to make that determination.

Below are a few simple “rule of thumb” methods to approach the assessment of what can be kept and what should be replaced:

Component	Reuse Feasibility	Considerations
Mounting Rail	Sometimes	Older rails may be usable, but new modules are often thinner (e.g. 35mm vs. 50mm), requiring all new clamps. Also consider spalling/mechanical damage, corrosion, rail spacing and mounting foot spacing (as per AS/NZS 1170).
Racking Hardware	Rarely	Older mid and end clamps are almost always incompatible with modern modules. Rail splices, tilt legs, or feet may also be non-compliant under current wind loading or corrosion standards.
Cabling	Case-by-case	Cabling may be reused if in good condition and compliant with AS/NZS 3000 and 5033. Note that old conduit or isolators may be degraded or undersized.
Inverters	Rarely	Inverter failure is often the trigger for repowering. Older models may not support modern grid codes or monitoring. If reused, check 4777.2 and DNSP requirements.
Modules	Sometimes	If only some modules have degraded or failed, partial reuse may be viable, but only if electrical characteristics (Isc, Voc) match and warranties are intact.
Monitoring	Case-by-case	Consider compatibility with new inverters and whether current systems meet reporting requirements.

Repowering Is a Strategic Decision

Repowering offers an opportunity to extend the life and improve the performance of a solar PV system, but it’s not as simple as replacing a few parts. The age and compatibility of existing equipment, the evolution of standards, and the economics of replacing versus repairing all influence the decision.

A successful repower requires a system inspection, a technical assessment, a financial model, and a strong understanding of compliance obligations. While reuse is possible, in many cases it may be more cost-effective and future-proof to start fresh — and design a system to current standards that will last another 20+ years.

Want help evaluating your solar asset for repowering? GSES offers system audits, end-of-life assessments, and design support to help asset owners and managers make informed decisions.
Visit www.gses.com.au or contact us at info@gses.com.au.