Technical expert report on defective photovoltaic installation in the Balearic Islands

If a photovoltaic installation in Ibiza, Mallorca, or the rest of the Balearic Islands clearly produces less than contracted, the key is not simply to demonstrate that it "generates few kWh." A solid technical assessment must reconstruct what performance was reasonably expected, compare that forecast with the actual production obtained, and determine why the difference exists: design, shading, electrical configuration, breakdowns, losses, equipment, unavailability, dirt, degradation, grid limitations, or a commercial estimate that was never technically achievable.

In a high-value facility—a luxury villa, a hotel, a resort, a warehouse, or a business self-consumption—a sustained difference between planned and actual production can translate into thousands of euros of unrealized savings, ungenerated surpluses, and a profitability very different from that which justified the investment.

At Optima Pericial, we conduct independent technical assessments in Ibiza and the Balearic Islands to analyze underperforming photovoltaic installations, identify the causes of the deficit, evaluate the technical solution, and quantify the damages when this is part of the commission. The report can be used to support negotiations, claims against the installer or an insurance company, or legal proceedings.

What does it really mean when a facility “does not produce what was contracted”?

Before stating that there is a breach of contract, it is necessary to define exactly what was promised.

Different concepts may appear in commercial documentation:

• Installed power in kWp.
• Estimated annual production in kWh.
• Projected annual cost savings.
• Percentage of self-consumption.
• Percentage of demand coverage.
• Estimated surpluses.
• Amortization period.
• Product or performance guarantees for certain equipment.

They are not equivalent. An installation can have exactly the contracted peak power and yet produce less energy than expected due to poor design. It can also produce the expected kWh and generate less cost savings because the actual consumption profile does not match the assumption used in the offer.

Estimated production is not the same as guaranteed production

An annual forecast depends on variables that change from year to year, especially irradiance and temperature.

Therefore, the expert report must analyze how the commercial figure was formulated: whether it was an indicative estimate, a simulation hypothesis, a contractual commitment, an express guarantee, or a piece of data used as an essential element to close the operation.

The legal assessment of that document is the responsibility of the lawyer, but the expert can determine whether the forecast had a reasonable technical basis and whether the assumptions used actually reflected the location.

Why a photovoltaic installation can produce less than expected

Incorrect design and sizing

An installation may be poorly sized with respect to the available space, consumption profile, inverters, string configuration, or electrical limitations of the site.

There may also be an incompatibility between installed DC power, inverter capacity and design strategy that causes losses greater than expected.

Orientation, tilt, and shadows poorly modeled

Shadows should be analyzed according to their geometry and evolution throughout the day and year. Chimneys, sheds, vegetation, parapets, architectural elements, or other rows of modules can reduce available energy.

The actual effect depends on the electrical configuration, power electronics, and module layout. Therefore, it is not technically correct to use a fixed percentage of loss for "having a shadow.".

Clipping or investor limitation

When the DC power of the photovoltaic field exceeds the instantaneous capacity of the inverter, there may be periods in which production is limited.

Oversizing DC/AC is not necessarily a mistake; it can be a reasonable design decision. The expert question is whether the ratio used was consistent with the offered output and whether clipping losses were correctly accounted for.

Poor electrical configuration

Improper distribution of modules in strings, voltages outside the optimal MPPT tracking range, imbalances, faulty connections, or insulation problems can affect performance.

Inverter failures or shutdowns

An inverter can record events, alarms, grid disconnections, thermal derating, power limitations, or intermittent faults.

Historical data from the investor and the monitoring portal can be an essential source for reconstructing periods of unavailability.

Dirt and maintenance

Dust, deposits, bird droppings or persistent dirt can reduce the effective irradiation on the modules.

In the Balearic Islands, environmental exposure must be analyzed in conjunction with cleaning frequency, rainfall, module tilt, and actual site conditions. Dirt may explain part of the deficit, but it should not be used as a general argument without quantifying its relevance.

Temperature and ventilation

The power output of a module varies with cell temperature. An installation with poor ventilation or thermal conditions different from those assumed may produce less than a simplified estimate.

Degradation or defect of components

Modules lose performance over time, but the analysis must distinguish between expected degradation and anomalous behavior.

It is not enough to measure a panel in the field and compare it directly to its nominal power rating on the technical data sheet, since that power rating is declared under standardized test conditions. To attribute a product defect, technically appropriate measurement procedures and conditions must be used.

External limitations to the installation

There may also be losses due to network incidents, limitation instructions, zero export, power restrictions, measurement errors, interruptions or communication problems that do not necessarily equate to a defect in the modules.

How can it be technically demonstrated that there is a production deficit?

An expert comparison should not be made solely between "promised kWh" and "metered kWh". The variables that influence the result must be normalized.

1. Reconstruct the actual system configuration

The expert identifies, according to the scope of the assignment:

• Number, brand, model and power of the modules.
• Brand, model and power of inverters.
• String and MPPT configuration.
• Orientation and inclination.
• DC and AC power.
• Optimizers or microinverters, if they exist.
• Battery systems.
• Export restrictions.
• Measuring and monitoring equipment.

2. Analyze the contract, the offer, and the preliminary study

The documents used to contract the installation are reviewed:

• Contract.
• Budget accepted.
• Memoir or project.
• Production studio.
• Economic simulation.
• Technical specifications.
• Commercial guarantees.
• Invoices.
• Start-up minutes.
• Emails and communications regarding incidents.

The goal is to find out what conditions the installer used to justify the investment and whether those conditions match what was actually done.

3. Analyze production history

Monitoring data allows us to study:

• Daily, monthly and annual production.
• Time curves.
• Stops.
• Alarms.
• Power cuts.
• Behavior of strings or MPPT when the platform provides that information.

It is important to preserve original exports, screenshots, and files before an account is modified, an investor is replaced, or access to the portal is lost.

4. Compare with irradiation and meteorology of the actual period

Annual production must be contextualized with the solar radiation actually available.

The PVGIS of the Joint Research Centre of the European Commission provides information on solar radiation and photovoltaic performance and can be one of the sources used as a reference, along with other available databases or measurements.

The comparison must be adapted to the exact period, location, orientation, and inclination of the installation.

5. Build a technical reference model

The expert can use appropriate simulation tools to reconstruct the expected behavior of the system under documented hypotheses.

PVsyst is a widely used tool in photovoltaic engineering, but it is not the only available tool, nor does its use automatically transform a simulation into conclusive evidence. What is relevant is the traceability of the input data, the assumed losses, and the comparison methodology.

6. Separate normal losses from abnormal losses

The balance sheet should consider factors such as:

• Temperature.
• Dirt.
• Shades.
• DC losses.
• Investor losses.
• Clipping.
• Availability.
• Degradation.
• Network or export limitations.
• Measurement errors.

Only after separating these factors is it reasonable to attribute part of the deficit to a design, execution, or equipment defect.

What tests can the expert perform on the installation

The tests depend on the observed problem, the power of the system, accessibility, and security conditions.

Technical visual inspection

Modules, structures, visible wiring, connectors, conduits, inverters, protections, panels and signs of overheating, deterioration, dirt or defective execution are checked.

Electrical checks

When appropriate and safe to perform, measurements of voltage, current, insulation, continuity or other quantities necessary to verify the behavior of circuits and equipment may be included.

The choice of tests must be adjusted to the configuration and regulations of the installation.

Curves IV

Characterizing current-voltage curves can help detect differences in behavior, losses, mismatches, or anomalies in modules or strings when performed under an appropriate methodology and the measurement conditions are corrected.

Thermography

Thermography can detect anomalous thermal patterns consistent with hot spots, diodes, connections, cells, or areas with different behaviors.

As with other expert reports, a thermal image must be interpreted technically and does not replace the causal diagnosis on its own.

Shadow analysis

This can be done using geometric surveying, solar tools, 3D models, hemispherical photographs, or other appropriate methods to determine when and how much each obstacle affects.

Technical regulations that may be relevant

The framework of a photovoltaic installation is not limited to a single standard.

Royal Decree 244/2019 on self-consumption

Royal Decree 244/2019 regulates the administrative, technical and economic conditions of self-consumption of electrical energy and remains in force with subsequent modifications, including an update published in March 2026.

It is a central standard for determining the self-consumption modality, the relationships between generation and consumption, and certain aspects of measurement, compensation, and management.

Low Voltage Electrotechnical Regulations

Royal Decree 842/2002 approves the Electrotechnical Regulation for Low Voltage.

In generating installations, ITC-BT-40, in addition to the other instructions that correspond to the characteristics of the installation.

Project, report, instructions and technical specifications

In a claim, general regulations can be just as important as the specific documentation of the installation: project or technical report, manufacturer's instructions, diagrams, configurations and warranty conditions.

The expert must distinguish between regulatory obligations, contractual requirements, and technical references. Not every technical recommendation is legally binding, but it may be relevant for evaluating the quality of the design or execution.

Legal framework: what can be claimed if the installation does not comply

The legal route depends on who contracted the installation, what was contracted, and what the cause of the problem is.

Breach of contract

Article 1101 of the Civil Code establishes liability for damages when, in the fulfillment of obligations, there is fraud, negligence, delay or contravention of the tenor of the obligation.

If the installation does not meet the agreed characteristics, was executed incorrectly, or an essential contracted service is not fulfilled, the contract and its associated documentation are the starting point for the claim.

Personal actions that do not have a special limitation period generally prescribe after five years from the date on which performance of the obligation can be demanded, in accordance with Article 1964.2 of the Civil Code. The specific calculation and the possible existence of special limitation periods must be legally reviewed for each case.

If the customer is a consumer: non-conformity regime

When the contracting party acts as a consumer or user, the Consolidated Text of the General Law for the Defense of Consumers and Users may be applicable.

This rule establishes that an incorrect installation can be equated to a lack of conformity when the installation has been carried out by the business owner or under their responsibility and is included in the contract for the sale of the goods.

For goods, Article 120 currently states that the business owner is liable for any lack of conformity existing at the time of delivery that becomes apparent within the following three years.

Businesses, hotels and economic operations

When the installation is contracted for a business or professional activity, the consumer regime may not be applicable.

In such cases, the contract, the agreed guarantees, the technical regulations, the commissioning documentation and the general rules of contractual liability become especially relevant.

The LOE does not automatically apply to any low-performance photovoltaic system

The fact that the panels are installed on a building does not mean that any production deficit is automatically subject to the liability periods of the Building Regulations Act.

The potential application of the Building Regulations Act (LOE) will depend on the nature of the work, its integration into the building structure, and the type of material damage claimed. A purely energy-related or contractual issue may require a different legal analysis.

Manufacturer commercial warranties

Manufacturers may offer commercial product or performance warranties with very different durations and conditions.

These warranties must be analyzed based on the specific conditions issued by the manufacturer for the installed model. There is no single legal term of "25 or 30 years" applicable to all modules, nor does a commercial warranty automatically replace any rights that may exist against the seller or installer.

The expert report as evidence

The Civil Procedure Law allows for the submission of expert opinions when technical knowledge is necessary to assess relevant facts.

Article 335 also requires that the expert state that he has acted and will act with the greatest possible objectivity, considering both what may favor and what may harm either party.

This is especially important in a performance assessment: the goal is not to "force" that every difference is the responsibility of the installer, but to technically separate justifiable losses from those that are not.

How is the economic damage quantified?

The quantification should not be limited to multiplying all the kWh not produced by the retail price of electricity.

Self-consumption that would have avoided the purchase of electricity

The energy that would foreseeably have been self-consumed can be valued by taking into account the cost of the energy that would have been avoided, using data from the period and a justifiable economic methodology.

Surpluses that would have been compensated or sold

The additional energy that would foreseeably have been surplus does not necessarily have the same economic value as the self-consumed energy.

A distinction must be made between instant self-consumption, compensation of surpluses, sale or other mechanisms applicable to the customer's contract.

Cost of repair or adaptation

Depending on the defect, it may be necessary to assess:

• String reconfiguration.
• Inverter replacement.
• Module repositioning.
• Incorporation or modification of equipment.
• Correction of protections or wiring.
• Replacement of defective modules.
• Monitoring repair.
• Access works and auxiliary means.

Future damages and lost profits

Future projections must be made with special caution.

It may require assumptions about production, degradation, availability, energy price trends, consumption profile, and remaining useful life. The longer the time horizon, the more important it is to explain the uncertainty in the calculation.

The admissibility and legal scope of each compensation concept must be coordinated with the lawyer who is handling the claim.

What should a photovoltaic expert report contain?

1. Subject of the opinion: technical issues that must be resolved.
2. Installation identification: location, power, components and configuration.
3. Documentation analyzed: contract, offer, project, studies, guarantees and data.
4. Methodology: inspection, tests, sources and tools used.
5. Production data: periods analyzed and quality of information.
6. Meteorological reference: irradiation and conditions used to normalize the comparison.
7. Expected production model: assumptions, losses and results.
8. Deviation analysis: difference between actual and reference production.
9. Causal diagnosis: identification and prioritization of causes.
10. Technical solution: actions necessary to correct the problem.
11. Economic valuation: if it is part of the order, traceable quantification of the damage.
12. Conclusions: clear answers to the expert questions.
13. Appendices: photographs, curves, data exports, diagrams and calculations.

Data that should be preserved before making a claim

If a conflict exists, it is advisable to preserve as soon as possible:

• Original contract and budget.
• Production and amortization study.
• Project or technical report.
• Invoices.
• Technical specifications.
• Equipment serial numbers.
• Guarantees.
• Monitoring credentials or exports.
• Monthly and daily historical data.
• Inverter alarms.
• Electricity bills before and after the installation.
• Communications with installer and manufacturer.
• Maintenance or repair parts.
• Photographs of the original state.

If the installer is going to replace equipment, reconfigure the inverter, or physically modify the installation, it may be especially important to preserve the data beforehand and document the existing state.

When is it appropriate to commission an expert report?

There is no need to wait until the facility stops producing completely.

It may make sense to request an independent review when:

• Annual production is persistently below the contractual forecast.
• The savings obtained are far removed from the study used to justify the investment.
• There are recurring alarms or shutdowns.
• The installer makes successive adjustments without resolving the deficit.
• It is suspected that the installed equipment does not match the contracted equipment.
• There are discrepancies regarding shadows or dimensions.
• A guarantee has been rejected.
• The insurer or the installer has issued a report with which you disagree.
• The investment is high and the damage accumulates month after month.

Cases of special interest in Ibiza and the Balearic Islands

High-value villas and homes

In villas with high energy consumption, air conditioning, swimming pools, pumps, electric vehicle chargers and other equipment, a photovoltaic installation can be part of a considerable energy investment.

The expert report must analyze not only the production of the modules, but also whether the economic study correctly represented the consumption profile used to promise the savings.

Hotels and tourist establishments

In a hotel, restaurant or tourist establishment, a relatively small percentage deviation can represent a relevant economic loss due to the size of the facility and the annual consumption.

Furthermore, the valuation must correctly distinguish between self-consumption, surpluses, seasonality, and occupancy periods.

Collective self-consumption

In a collective facility, it may be necessary to separate two issues:

• If the plant generates the technically expected energy.
• If the energy produced is being allocated and accounted for correctly among the associated consumers.

Royal Decree 244/2019 regulates collective self-consumption and energy distribution, so an incident of coefficients or measurement can generate a problem different from a physical production defect.

Mistakes that can weaken the claim

Comparing different years without correcting for irradiation

A year with less solar resource cannot be directly compared to an average figure without normalization.

Assuming that all losses are the fault of the panels

The deficit may lie in the design, investor, strings, shadows, limitations, availability, measurement, or even in a mistaken economic assumption.

Modify the installation before documenting it

A reconfiguration or replacement can eliminate evidence about the state that originated the conflict.

Use only screenshots from one app

Screenshots are useful, but whenever possible, exports, original files, invoices, and other data that allow the historical record to be reconstructed should be preserved.

Automatically apply a manufacturer's warranty

A module performance warranty does not necessarily cover poor installation design, shading, configuration errors, or an incorrectly sized inverter.

Confusing production with profitability

An installation can produce correctly and not achieve the commercially promised savings if the assumptions regarding price, self-consumption or consumption profile were unrealistic.

Why choose Optima Pericial?

A relevant photovoltaic claim requires combining electricity, solar generation, data analysis, contractual documentation, and economic valuation.

At Optima Pericial we approach the assignment from an independent position:

• We reviewed what was contracted.
• We reconstructed the installation that was actually carried out.
• We analyze the production data.
• We compared the weather and the losses.
• We determine the technically justifiable causes.
• We assess the repair when it is appropriate.
• We quantify the damage if it is part of the assignment.
• We prepare a report that is easy to understand for installers, insurers, lawyers, and courts.

The goal is not to claim that every facility that produces less than a forecast is poorly executed. The goal is to determine what is actually happening and turn that conclusion into traceable technical evidence.