End of Warranty in Renewable Assets: How to Reduce Environmental and Operational Risks in Wind, Solar and BESS in Europe

When a wind farm, a solar plant or a large Battery Energy Storage System (BESS) approaches the end of its warranty period, something quietly shifts in the background. What used to be a contractual discussion with the manufacturer becomes a direct balancing act between operations, environment, insurance and financial performance. A critical failure is no longer just a technical issue: it can mean an oil spill in an agricultural area, a fire with local impact, extended downtime during periods of high power prices, and tense renegotiations with insurers.

At the same time, these assets are no longer “new”: turbines are often 10–15+ years old, inverters have gone through their first lifecycle, and batteries are starting to lose capacity while PPAs still have many years to run. In practice, the end of warranty marks the beginning of a more complex chapter in the lifecycle of renewable assets, and this is precisely where smart use of data, AI and predictive maintenance can make the difference between operating at the edge of risk and turning this phase into a competitive advantage.

What really changes when the warranty expires?

During the warranty period, OEMs absorb a large part of the impact of manufacturing defects. In offshore wind turbines, for example, five-year warranties are common, where a faulty gearbox or a generator with a serial issue is repaired or replaced at no direct cost to the operator. In many cases, these events appear as provisions or losses in the OEM’s own financial statements.

Once that period ends, the logic flips. Every failure turns into a direct cost: spare parts, crane mobilisation, outage time and lost revenue. For solar inverters with typical warranties of 5–10 years, the transition is similar: from the end of coverage onwards, a serial failure can easily wipe out the operating profit of an entire year. In BESS, the mismatch is even more evident: many batteries come with a guaranteed life of around a decade, while power offtake contracts often run for 20–30 years. In practice, from day one it is clear that battery replacement will be an inevitable event in the economic life of the project.

This shift is not only technical or financial. Once the warranty expires, the risk profile changes. Insurers adjust premiums and conditions, lenders look more closely at failure history and maintenance records, and the operator can no longer rely on a “direct line” with the OEM for everything. This is exactly the moment when the level of maturity in data management and plant monitoring becomes decisive.

End of warranty under regulatory and environmental pressure

The warranty may end, but regulatory obligations do not. Across Europe, the pressure to maintain high standards of safety, reliability and sustainability continues — and tends to intensify as the renewable fleet ages.

The new EU Battery Regulation is a clear example. It raises the bar across the entire value chain, from design to end of life, requiring CE marking and clearer criteria for safety, performance and circularity in energy storage systems. A BESS installed a few years ago can suddenly find itself facing the need for engineering upgrades, new studies and potential re-certification to remain compliant with the latest requirements.

In wind and solar, the picture is similar. The Green Deal targets and national climate policies do not distinguish between new and mature assets: all of them need to operate safely, efficiently and in line with increasingly strict environmental standards. Countries like the UK have been publishing specific guidance on safety for grid-scale BESS, bringing fire and rescue services, local planning authorities and environmental agencies into the conversation on permitting and ongoing operation of these systems.

The message is straightforward: even if, from a contractual point of view, the OEM is no longer liable for that equipment, from a legal and environmental perspective the operator remains fully responsible. An oil spill, a fire or a structural failure in an 18-year-old turbine will be treated with the same seriousness — or more — than in a newly commissioned project. That is why the post-warranty operating plan needs to be designed as a chapter of its own in the strategy, not just as the inert continuation of what was being done before.

Ageing assets and rising environmental risks

As time goes by, the “clean energy” image coexists with environmental risks that become more relevant if maintenance fails to keep pace with the ageing of equipment.

One of the most visible examples is oil leakage in turbines and transformers. Wind turbines hold hundreds of litres of lubricants and hydraulic fluids in gearboxes, pitch and yaw systems and transformers. Seals, hoses and connections suffer from fatigue, vibration and temperature variations. Small cracks can turn into constant drips that first stain the tower and then the soil around it. If they are not detected and contained quickly, these leaks can reach watercourses, farmland and aquifers, turning a mechanical issue into an environmental and regulatory liability — with the potential for fines and significant remediation obligations.

At the same time, oil accumulated in nacelles and electrical compartments increases the risk of fire, especially in older turbines that were often designed without automatic fire suppression systems. A short circuit or a seized brake can be enough to trigger an incident. In BESS, the risk manifests differently: thermal runaway in degraded lithium-ion cells can lead to long-lasting, hard-to-extinguish fires, releasing fumes with chemicals of concern for environmental and public health authorities.

These events remain rare in statistical terms, but each one of them has a disproportionate impact. A fire at a battery installation under commissioning in England, for example, led the fire service to adopt a strategy of controlling the perimeter and monitoring the fire, letting the system burn down until the risk of explosion was reduced. In solar plants, large-scale fires can melt hundreds of modules and expose potentially toxic materials, contaminating soil and water.

On top of that comes the question of waste. Degraded batteries and damaged PV modules must be managed as industrial waste, in line with strict rules for transport, storage and final disposal. If the end of warranty is not accompanied by a clear plan for this phase, there is a real risk of turning an asset designed to deliver environmental benefits into a source of contamination and local conflict.

What the data tells us about post-warranty failures

When you look at the failure rate over the lifetime of renewable assets, a pattern appears frequently: after the first 5–10 years, corrective maintenance curves start to rise. This trend is reflected in turbines with a greater number of unplanned outages, inverters with cascading failures and storage systems that require more frequent interventions to keep performance within design limits.

Reliability studies show that corrective maintenance cost per kW increases with turbine age, and European operators report, from experience, that components such as gearboxes, main bearings and PV inverters become more failure-prone as the plant gets older, especially if they have not gone through major retrofits or upgrades. In practice, a wind farm that used to run close to 98% availability in its early years may drop to 95% or less after 15–20 years, with a direct impact on energy yield and return on investment.

In parallel, the insurance sector has been watching more dramatic incidents closely, such as onshore and offshore turbine collapses after many years in operation. Although the causes vary — combining design, manufacturing, extreme loads and maintenance — the message is the same: in mature assets, small cracks or structural issues that go undetected can evolve into catastrophic failures, with environmental damage, safety risks and large material losses.

For BESS, the absolute number of severe incidents is still relatively small, but each case triggers code updates, technical debate and adjustments to design standards. Authorities acknowledge that public databases on storage system fires still have gaps; as a result, every documented case carries disproportionate weight in shaping engineering practice and operational “good practice”.

All of this reinforces a central idea: the post-warranty phase is not simply “more of the same” in terms of risk. It behaves as a distinct stage, with its own combination of failure probabilities and potential impacts — which demands dedicated models for monitoring, maintenance and insurance pricing.

How data and AI turn the post-warranty phase into a competitive advantage

If the post-warranty phase concentrates more technical, environmental and financial risk, it also offers more room to differentiate mature operations from those constantly “putting out fires”. This is where data and AI-driven approaches, like the ones Delfos has been deploying with operators in Europe, become highly relevant in practice.

A first step is to treat the end of warranty as a project, not just a date in the schedule. Well-structured End of Warranty inspections, combined with historical operating data, make it possible to identify latent defects that are still the manufacturer’s responsibility and, at the same time, to establish a clear baseline of each asset’s “health”. When this information is integrated into a platform that consolidates SCADA, CMS, maintenance records and field reports, the operator moves away from gut-feel and starts building multi-year O&M plans on hard evidence.

From there, predictive monitoring becomes the core of the strategy. In portfolios that combine wind, solar and BESS, it is essential to have an integrated view of risk, where AI models analyse patterns in vibration, temperature, pressure, current and performance to flag components in degradation well before failure. Anticipating a problem in a bearing, an inverter or a battery module is not just about avoiding a high repair bill: it is about reducing the probability of a serious environmental incident, such as a major oil leak or a thermal-runaway event.

Data also changes how retrofits and upgrades are decided. Instead of relying only on generic OEM recommendations, the operator can compare scenarios: running equipment to failure versus replacing it preventively; accepting a degrading performance curve versus implementing a firmware update that improves efficiency and reduces mechanical stress. The platform translates these choices into recovered MWh, reduced downtime and P&L impact, helping build robust business cases for life-extension and modernisation investments.

Finally, the same data infrastructure that supports O&M decisions serves as the backbone for governance. Incident response procedures, inspection records, alarm logs and automated reports form a history that can be presented to regulators, insurers and local communities as evidence of due diligence. In a context where post-warranty responsibility is under increasing scrutiny, that level of transparency becomes an asset in itself.

Post-warranty as a test of sector maturity

The end of the warranty is not the end of the story for a renewable project; it is the point where the sector shows how mature it really is. This is the phase where it becomes clear whether the operation was designed just to “keep the asset running” or to manage, intelligently, the full lifecycle — from the first MWh to responsible decommissioning.

On one hand, operational and environmental risks do increase with age; on the other, there have never been so many tools to control them: more accessible sensors, more accurate predictive models, platforms capable of integrating wind, solar and BESS data and turning it into day-to-day decisions. When operators and investors embrace this view and accept that the post-warranty phase requires its own planning, the result is a virtuous combination of greater safety, more financial predictability and stronger alignment with ESG commitments.

Seen from this angle, the date when the warranty expires stops being a simple worry in the calendar and becomes a milestone: the moment when the operation fully assumes responsibility for what it has built and proves it can keep those assets delivering clean energy with confidence and accountability right up to their last day in service.

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