The Hidden Cost of Cutting Solar Maintenance: A USD 15,000 Lesson
Solar PV systems are widely recognised as low-maintenance assets. However, "low maintenance" does not mean "no maintenance". Without regular performance monitoring and timely cleaning, energy losses can accumulate gradually and remain unnoticed for months. In some cases, accumulated soiling could cause permanent damage to the panel surfaces.
This case study demonstrates how a routine maintenance activity prevented a significant financial loss for an industrial rooftop PV system.
The site is a 600 kWp rooftop solar PV system commissioned in Q2 2023.
Like many commercial and industrial (C&I) solar asset owners, the customer's primary focus was not on how the solar system was performing, but on running their core manufacturing business. As long as the inverter monitoring portal indicated that the system was operating normally, generating electricity, and reporting no alarms, there was little reason to suspect that significant performance losses were developing.
However, inverter monitoring platforms are primarily designed to report equipment status rather than evaluate system performance. They can confirm whether an inverter is online, but they cannot determine whether the system is generating as much energy as it should under the prevailing weather conditions.
No dedicated performance analytics or energy loss assessment had been implemented. Consequently, the gradual reduction in energy yield caused by module soiling went unnoticed. Although the owner could compare annual generation from one year to the next, it was impossible to determine whether any reduction was caused by weather variation, seasonal effects, or an underlying performance issue.
From an operational perspective, the system appeared healthy. In reality, hidden performance losses had been accumulating for months.
Figure 1: PV Health Scan - inverter daily spatial heatmap identifying underperforming areas
In late 2025, the owner requested a performance assessment using the PV Doctor Smart O&M Platform.
Rather than relying solely on inverter status or energy production, PV Doctor compared the site's actual generation against satellite-derived irradiance data and analysed historical performance trends. PV Doctor's PV Health Scan (Figure 1) overlays inverter performance onto satellite imagery, allowing underperforming areas to be identified spatially rather than through spreadsheets or trend charts alone.
The assessment identified a consistent reduction in energy generation that could not be explained by weather conditions. PV Doctor team later found out more complex issues. To verify the underlying causes, the investigation was extended with on-site inspection and AI-assisted aerial thermal imaging.(Figure 2)
Further analysis indicated that the primary cause was excessive module soiling and seasonal partial shading. Some were spotted visually, while others were detected by AI-detection thermal aerial imaging.
Figure 2: AI-assisted Thermal Aerial Inspection for Hotspot Detections
Table 1: Summary of Thernal Inspection Findings - Affected PV Modules
Table 2: Summary of Thermal Inspection Findings - Affected PV Strings
Thermal inspection was conducted to validate the performance anomalies identified during the PV Health Scan and to determine whether the losses were associated with localised module defects or broader system-wide issues. The inspection revealed that only 10.8% of PV modules exhibited observable hotspots, excessive soiling, or other thermal abnormalities. At first glance, this may appear to be a relatively small proportion of the total installation. .
However, these affected modules were distributed across 73% of the PV strings. Because PV modules are electrically connected in series, the performance of an entire string is constrained by its weakest-performing module. Consequently, even a limited number of defective or heavily soiled modules can reduce the energy production of a much larger section of the plant.
This finding highlights an important principle in PV system operation:
A small number of affected modules does not necessarily translate into a small energy loss. Their location within the electrical configuration is equally important.
Based on PV Doctor's performance analytics, thermal inspection, and site investigation, the major sources of energy loss were quantified and prioritised. The results indicate that the site's reduced energy production was primarily driven by avoidable performance losses, with soiling and seasonal shading accounting for the majority of the identified loss mechanisms.
- Estimated Annual Performance Loss: 11%
- Estimated Soiling Loss: 5%
- Estimated Shading Loss: 6%
These quantified losses provide the technical basis for evaluating maintenance priorities and estimating the financial benefit of corrective actions.
The financial consequences were more significant than initially expected.
Figure 3: Performance Ratio (PR) Evolution and Projected No-Clean Scenario
Based on the site's electricity tariff and expected annual generation, the accumulated performance losses were estimated to exceed USD 15,000 per year. Although the system remained operational throughout the period, reduced energy production gradually eroded the financial return of the solar investment.
A. Operational Impact
Table 3: Operational Performance Comparison: Clean vs. No-Clean Scenario
No major inverter failures or system availability issues were identified. Instead, the investigation showed that the losses were primarily attributable to avoidable performance-related factors, particularly module soiling and seasonal partial shading.
To quantify the financial value of corrective action, PV Doctor compared the actual operating performance following the cleaning programme against a projected scenario in which no cleaning was carried out during the same period.
B. Financial Impact
Table 4: Financial Evaluation of the Cleaning Intervention (3-Month Period)
Over the three-month period following the recommended cleaning, the site generated an estimated USD 3,753 in additional electricity revenue compared with the projected no-clean scenario. After accounting for the cleaning cost of approximately USD 760, the intervention delivered a net financial benefit of USD 2,993.
C. Investment Metrics
Table 5: Investment Metrics of the Recommended Cleaning Programme
The financial return demonstrates why cleaning should be evaluated as an investment rather than an operating expense.
In other words, every USD 1 invested in cleaning protected nearly USD 5 of electricity revenue and generated almost USD 4 in net financial value.
Based on the performance assessment, the owner carried out the recommended cleaning programme. Within days, system performance recovered noticeably, confirming that the lost generation was largely attributable to soiling rather than equipment failure.
The site was subsequently onboarded to the PV Doctor Smart O&M platform for continuous performance monitoring, allowing future abnormalities to be identified before they develop into significant financial losses.
Figure 4: Annual Energy Generation Before and After Performance Optimisation
Looking at annual generation, 2024 was 787.0 MWh, then dropped to 769.9 MWh, which was 2.2% and was higher than normal degradation. After subscribed to PV Doctor and followed 2 cleaning cycle suggestions, based on weather-normalised performance, the system is projected to close CY2026 at approximately 788.8 MWh, representing its highest annual generation since commissioning.
One of the most important lessons from this case is that reducing maintenance costs can increase energy losses and reduce overall profitability.Cleaning is often viewed as an operational expense. In reality, it protects revenue.
In this case, the annual cost of routine cleaning and performance monitoring represented less than 10% of the financial loss caused by neglected maintenance. For many commercial and industrial solar assets, the question is not:
"How much does cleaning cost?"
The more important question is:
"How much revenue is lost by delaying it? Or by reducing the frequency?"
This is the principle we will explore further in our next article, where we examine the economics of solar panel cleaning and introduce a simple framework for determining when cleaning creates positive financial value.
The objective of solar asset management is not to minimise maintenance expenditure. It is to maximise lifetime financial return. Achieving that requires maintenance decisions to be driven by performance data rather than fixed schedules or assumptions.
PV Doctor Pte. Ltd. ("PV Doctor") is a leading solar asset performance management provider which has surpassed 2 GWp of assets under monitoring (AUM) in May 2026, after just 14 months of operations. The company currently monitors over 2,000 systems across 22 countries, reinforcing its rapid expansion and growing relevance across both emerging and mature solar markets.
In addition, PV Doctor just published the very first Singapore PV Benchmarking Report, documenting the true PV systems performance of PV systems in year 2025. Notably, PV Doctor monitors around 1,000 PV systems in Singapore.
With the support of its Board of Directors, International Advisory Panel, investors, and partners, PV Doctor will continue advancing data-driven diagnostics, performance optimisation, and Smart O&M solutions to help solar asset owners improve their energy yields.
