7 Checks Before an O&M Contract to Ensure Declines in Power Generation Are Not Overlooked

When you feel that a solar power generation system is producing less electricity, the cause is not necessarily a single one. Weather, season, shading, soiling, equipment outages, measurement deviations, output control, insufficient contractual verification, and other factors can combine to make it appear that generation has declined. Especially before entering into an O&M contract, if you entrust maintenance without fully confirming the inspection items and reporting scope, you may fail to detect early signs of abnormalities, and discovery of generation losses may be delayed.

O&M is an important framework for keeping equipment safe and continuously monitoring power generation status. However, signing a contract does not automatically mean that all drops in generation will be detected. It is important to clarify before signing the contract which data will be monitored, how frequently checks will be performed, who will make judgments when anomalies occur, and to what extent on-site inspections will be conducted.

This article explains seven perspectives to check before entering into an O&M contract for practitioners searching for "low power output". It summarizes, in a format that's easy to use in the field, not only the key points to consider when comparing contract terms but also the practical approaches you should understand to avoid overlooking declines in power output.

Table of Contents

• Confirm how to define a decrease in power generation prior to contract signing.

• Confirm the scope and frequency of monitoring data review

• Confirm the criteria for determining anomalies and the notification rules

• Confirm the scope of checks to be performed during the on-site inspection.

• Confirm whether the cause of the decrease in power generation can be traced in the report.

• Confirm the process for work outside the scope of the contract and for handling additional requests.

• Check whether we can receive long-term improvement proposals

• Summary

Confirm how to define a decrease in power generation before contracting

The first thing to confirm before entering into an O&M contract is the criterion for judging when "generation is low." Power generation varies greatly depending on solar irradiance, ambient temperature, season, tilt angle, orientation, and the surrounding environment. Therefore, simply being lower than last month or lower than the same month last year cannot be conclusively called an anomaly. If you do not clarify before contracting how a decline in generation will be judged, an actual decrease may be overlooked as "weather-related."

In practice, it is important not only to look at the power output itself, but also to check how much power is being generated relative to solar irradiance, whether there are differences between systems or power conditioners within the same plant, and whether anything seems off compared with past days under the same conditions. For example, the suspected causes differ when the overall generation is low on a sunny day versus when only some circuits show reduced output. If the entire plant’s output is low, you need to check solar irradiance conditions, output control, overall equipment settings, and constraints on the receiving-side equipment. On the other hand, if only a specific string or particular device is underperforming, consider local abnormalities such as a broken cable, poor connections, shading, soiling, or equipment shutdown.

In an O&M contract, it is important to clarify how far such judgments will be taken. Whether the scope is simply to monitor a remote screen and notify you when an alarm appears, or to review daily generation trends to detect anomalies, will affect how easily a drop in generation is identified. Before signing the contract, confirm the reference baselines that will be used to determine a generation decline. Such baselines include design-expected generation, past performance, comparisons with nearby systems or within the same facility, generation efficiency adjusted for solar irradiance, and equipment-level output differences.

Be careful not to rely too heavily on comparisons with the expected power generation. The assumptions used at the design stage are guidelines based on certain premises. In actual installations, factors such as year-to-year weather variability, changes in the surrounding environment, soiling of panel surfaces, growth of vegetation, snowfall, tilt of the mounting structure, and aging of equipment will have an impact. Before signing a contract, confirm how differences between expected and actual values will be handled and at what stage such differences will be investigated, as this will reduce the likelihood of misunderstandings later.

Also, when you receive a report that "power generation is low," it is important to confirm the order in which the O&M company will carry out its checks. If the contract defines a clear flow—from checking weather data, checking remote monitoring data, checking equipment alerts, deciding whether an on-site inspection is necessary, through to preparing a report—then drops in power generation can be traced by procedure rather than by intuition. Conversely, if the decision criteria are left vague in the contract, even if a decrease is noticed it can take time to begin an investigation.

In pre-contract meetings, it is important to confirm not only "how much of a drop in power generation will be treated as an anomaly" but also "what the decrease will be compared against when making that determination." Simply having this perspective makes an O&M contract more likely to function not as a mere request for maintenance inspections, but as a management system for detecting power generation losses early.

Confirm the scope and frequency for reviewing monitoring data

To avoid missing a drop in power generation, it is important to determine the scope and frequency at which monitoring data are checked. Even with an O&M contract, the monitoring content varies depending on the agreement. Some contracts involve checking generation status daily, while others only respond when an abnormal alert is issued. Contracts centered on monthly reports can take time to detect subtle day-to-day declines.

In solar power generation, decreases in output can sometimes appear suddenly within a single day, while other times they progress gradually over weeks or months. For example, anomalies such as equipment shutdowns or breaker trips are relatively conspicuous. On the other hand, accumulation of panel soiling, increasing shading from vegetation, deterioration of connectors and wiring, and subtle changes in mounting structures can all have a gradual impact on output. Because these slow declines are difficult to detect with single, isolated alerts alone, management that monitors trends is necessary.

Before signing a contract, specifically verify the data that will be checked. Whether you examine only the power plant’s total generation, look at each power conditioner, or can inspect down to the string or circuit level will affect the accuracy of anomaly detection. If you only look at total generation, a decline in some circuits can be masked by generation from other circuits. Especially in large installations, overall figures alone make it difficult to grasp localized generation losses.

Monitoring frequency is also important. With daily monitoring, you can quickly notice a sudden drop on a sunny day. With weekly monitoring, it becomes easier to track trends over a period of several days. With monthly monitoring, you can detect major drops in power generation, but it can be difficult to pinpoint when they occurred. Before signing a contract, you need to consider which frequency matches your company's equipment scale and risk profile. For installations where power output is critical, too low a monitoring frequency can lead to significant generation losses before an anomaly is detected.

Also, in addition to simply viewing monitoring data, you should confirm how to handle data gaps and communication failures. If remote monitoring stops, you need to determine whether generation has actually ceased or whether the issue lies with the monitoring equipment or the communication link. If there are periods when monitoring data cannot be obtained, you cannot accurately assess the drop in power generation during those periods. Before signing a contract, it is advisable to confirm the contact criteria, recovery verification, and whether on-site inspection is necessary in the event of communication failures.

Furthermore, it is important to consider how much to account for solar irradiance and weather conditions. To determine the cause of low power generation, you need to look not only at the generation output itself but also at the day's weather and solar irradiance conditions. It is natural for generation to be low on rainy or cloudy days, but if output does not increase despite clear skies, this warrants attention. On hot days, photovoltaic modules tend to have reduced output due to their characteristics. Judging solely by generation output without taking these conditions into account can lead to overlooked anomalies or incorrect assessments.

Before entering into an O&M contract, it is important to confirm whether the monitoring service will "only receive data" or will "read the data and assess the likelihood of abnormalities." To avoid overlooking a decline in power output, it is desirable to have a system that can view power output, equipment condition, solar irradiance conditions, communication status, and historical trends in combination.

Confirm the criteria for anomaly assessment and the notification rules

When a decrease in power generation is suspected, the next important matter is the criteria for determining abnormalities and the communication rules. In an O&M contract, it is important not only to detect abnormalities but also to specify who to notify, when to notify them, and what information to provide after detection. Even if there are signs of abnormality, if the notification criteria are unclear, responses can be delayed or stakeholders may disagree on the judgment.

First, what needs to be confirmed is which conditions should be treated as abnormalities. There are many types of anomalies: power conditioner stoppage, communication failures, sudden drops in power generation, output discrepancies in specific circuits, occurrence of alerts, and mismatches between sold electricity and generated electricity. Rather than treating all of these with the same level of urgency, it is necessary to prioritize them according to their impact and safety. For example, the urgency of notification differs between a complete facility shutdown and a slight reduction in output in part of the system.

In communication rules, the timing of the initial report is particularly important. Whether you notify on the same day a drop in power generation is confirmed, wait a certain period to observe before notifying, or summarize it in a monthly report will change how quickly response actions begin. Early notification is necessary when there is a stoppage of power generation or a large decrease. On the other hand, if every temporary fluctuation caused by weather is reported as an emergency, the burden on the responsible staff increases and important abnormalities can become buried. Before contracting, it is easier to operate if you separate abnormalities that should be reported urgently from those to be handled in regular reports.

Also, check the quality of the communication. A report that simply says "power generation is low" does not allow you to decide what to do next. In practice, you need information such as when the decline began, over what area it is occurring, whether it appears abnormal given the weather and solar irradiance conditions, whether an on-site inspection is necessary, and what provisional causes can be considered. If these points are organized at the time of the initial report, the power plant operator and the managers will find it easier to make subsequent decisions.

Before entering into a contract, contact points and the division of responsibilities must also be clearly defined. If you do not clarify who within the company should be contacted, how to handle contact on holidays and at night, who makes decisions in emergencies, and who authorizes on-site dispatch, response after an anomaly is discovered can come to a halt. In facilities with multiple stakeholders in particular, there can be many parties involved — the owner, the management company, the contractor, the chief electrical engineer, the insurance point of contact, and so on. The more complex the lines of communication, the more important it is to sort them out before contracting.

In anomaly assessment, it is also important to avoid excessive certainty. Remote monitoring alone does not necessarily allow the cause to be identified completely. Whether a drop in power generation is caused by equipment failure, shading, soiling, or a measurement issue may require on-site inspection or additional data. When receiving communications from the O&M company, asking them to report confirmed facts separately from suspected causes rather than making definitive statements makes it easier to prevent incorrect judgments.

To make an O&M contract that does not overlook declines in power generation, a system for reporting anomalies as well as a system for detecting them is essential. Before signing the contract, confirming the criteria for determining anomalies, the classification of urgency, the timing of the initial notification, the information to be communicated, and the roles of the parties involved will make it easier to prevent the escalation of power generation losses.

Confirm the scope of checks for the on-site inspection

Remote monitoring alone may not be sufficient to fully grasp the causes of reduced power generation. Therefore, before entering into an O&M contract, confirm how thoroughly on-site inspections will verify conditions. Many causes of low power output cannot be determined from on-screen figures alone. Panel soiling, shading from vegetation, bird damage, fallen leaves, snow accumulation, racking tilt, cable damage, anomalies around junction boxes, and discrepancies between on-site displays and monitoring data are often difficult to assess without actually visiting the site.

The scope of on-site inspections varies depending on the contract. You need to confirm whether the work is limited to a visual check, includes electrical measurements, involves photographic records, or focuses on locations suspected of reduced power output. To avoid overlooking a decline in power generation, it is important not just to walk around the equipment once, but to verify by correlating generation data with on-site conditions. For example, if a particular circuit shows low output, concentrating checks on the string of panels or connection points corresponding to that circuit makes it easier to pinpoint the cause.

Shadows from vegetation are an often-overlooked factor causing reduced power generation. Even if there was no problem at the time of contract, vegetation can grow with the seasons and over the years, casting shadows in the mornings and evenings or during winter. If low power output is concentrated in the morning and evening hours, surrounding trees, fences, buildings, utility poles, overhead lines, or mountain shadows may be having an impact. During on-site inspections, it is important not only to check the time of inspection but also to verify while considering the times and seasons when shadows are likely to occur.

Dirt and deposits also affect power generation. When sand dust, pollen, bird droppings, fallen leaves, mud splashes, remnants of snow, or the like are on the panel surface, power output may decrease. The effect of soiling can appear uniformly across the entire system or be biased toward certain rows or specific panels. Before signing an O&M contract, it is advisable to confirm whether soiling will be included as an inspection item and how cleaning proposals and implementation decisions will be handled.

Checking electrical equipment is also important. The condition of junction boxes, combiner boxes, power conditioners, circuit breakers, terminal connections, cables, and grounding-related equipment can affect power output and safety. However, inspecting these requires specialized knowledge and safety management. Before signing a contract, it is important to confirm the inspector’s qualifications and experience, the scope of measurement work, whether work that involves a power outage is permissible, and the procedures to follow if an abnormality is found. Forcing an inspection or performing inappropriate work may instead lead to accidents or equipment failures.

At on-site inspections, having photographic records is also important. If you photograph areas suspected of causing a drop in power generation, it will be easier to check the situation later. Recording at fixed points the growth of vegetation, dirt on panel surfaces, the condition of mounting racks, equipment displays, warning indicators, and cable conditions makes it easier to compare with the past. Before signing a contract, confirming what will be photographed, how photos will be included in reports, and how long they will be retained will help with later explanations and decisions on improvements.

In O&M contracts, not only the frequency of on-site inspections but also the quality of those inspections is important. Don’t judge solely by how many inspections are performed per year; confirm which items will be checked, from what perspectives, and to what extent in order to detect decreases in power generation. When remote monitoring and on-site inspections are integrated, it becomes easier to quickly narrow down the causes of low power output.

Confirm whether the cause of reduced power output can be traced from the report

Before entering into an O&M contract, you should also check the contents of the reports that will be submitted. Reports are not merely inspection records. They are documents for detecting signs of declining power generation, tracing causes, and making decisions about corrective measures. If a report remains superficial, it becomes difficult later to confirm "when the decline began," "what caused it," and "which response should have been taken."

Reports that are useful when you suspect low power generation organize trends in generation, generation status by equipment, presence or absence of abnormal alerts, on-site inspection results, photos, findings, and recommended actions. What is particularly important is that they do not merely list numbers but describe how those numbers were interpreted. Even if generation is lower than the previous month, if weather factors are significant it may not be considered abnormal. On the other hand, if generation is low relative to solar irradiance conditions, or if only part of the same installation shows a decrease, there may be an anomaly.

In reports, including comparisons at the equipment and circuit levels as well as total generation makes it easier to trace the cause. For example, information that only shows total facility generation is lower than the same month last year makes it difficult to determine whether it’s due to weather or equipment malfunction. However, if you have generation by power conditioner, differences between strings, downtime, and alert history, it becomes easier to narrow down where the problem lies.

Also, in reports it is important not simply to write "no abnormalities" but to clearly specify the scope of what was checked. For reports concerning a decline in power generation, it must be clear what period of data was reviewed, which equipment was inspected, which locations were checked on-site, whether measurements were taken, and what conditions can be verified from photographs. If the scope of inspection is unclear in a report, then when a problem occurs later it will be impossible to determine whether it was an oversight or outside the contract scope.

The way findings are written is also important. Because the cause of reduced power generation is often not attributable to a single factor, reports are more useful in practice if they separate confirmed facts, presumed causes, and items requiring further verification. For example, if organized in a form such as "Power output is low on specific equipment," "No communication anomalies were confirmed on the same day," "No major damage was observed in the on-site visual inspection," and "Electrical measurements are required for detailed inspection," it becomes easier to make the next decision.

We recommend checking a sample report before signing a contract. By reviewing a sample you can confirm how thoroughly the analysis of power generation decline is covered, whether it includes photographs, whether it offers improvement recommendations, and whether it avoids excessive technical jargon so it’s easy to use for internal explanations. If the report is hard to understand, the staff responsible will have a greater burden of preparing additional materials when explaining it internally. When addressing decreases in power generation, not only on‑site technical judgments but also internal approvals and cost decisions are required, so the clarity of the report is important.

Confirm not only the monthly reports but also the format for abnormal-event reporting. Even if there are no major issues in regular reports, when a decrease in power generation is suspected, a more detailed root-cause analysis and response plan than usual may be required. Before signing the contract, check whether a separate report will be issued for abnormal events or whether it will be appended to the regular report, and whether photos and data can be attached; doing so will make responses smoother.

Reports are a part of operations where an O&M company's service quality becomes evident. To avoid overlooking decreases in power generation, confirm that reports not only record the facts of inspections but also link generation data with on-site conditions so causes can be traced.

Confirm the process for handling work outside the contract scope and for additional work

In O&M contracts, it is important to clearly define which tasks are included and which are not. Even if a drop in power output is detected, subsequent investigation, repairs, cleaning, vegetation control, parts replacement, electrical measurements, manufacturer support, or insurance handling may not be covered by the contract. If you sign without confirming the scope, it may take time to move on to the next steps even after an anomaly is discovered.

Low power generation may sometimes be revealed by remote monitoring, but on-site inspection or additional measurements may be necessary. For example, if a device has stopped, this can be detected via remote monitoring, but confirming whether the stoppage is due to an internal fault, an abnormality in peripheral equipment, or the operation of a protective device may require on-site verification. Even when a drop in output is suspected for a particular string, the cause cannot be identified without checking connections, cables, panels, shading, soiling, and the like.

Before signing a contract, confirm the procedure for any additional measures that may become necessary. After an anomaly is detected, you need to clarify who will decide whether to dispatch personnel to the site, when estimates and approvals will be made, whether urgent advance action can be taken, and how reporting after the work will be handled. If the response process is not decided, the time from confirming a drop in power generation to restoration may be prolonged, increasing potential generation losses.

What you should pay particular attention to is the distinction between minor tasks and specialized tasks. Visual inspections on site and simple recovery operations may be covered under the contract, whereas electrical measurements, parts replacement, work requiring equipment shutdown, insulation checks, and repairs to connection points may require separate arrangements. These involve safety, qualifications, and scopes of responsibility, so they need to be clarified before contracting. Even if the cause of a decline in power generation is identified, you may not be able to restore it on the spot without the authority to do so.

Also, you should confirm how vegetation control and cleaning are handled. Shadows from plants and panel soiling can lead to reduced power generation, but whether vegetation control and cleaning are included in the O&M contract depends on the contract terms. Even if they are not included, you should check whether the contractor will identify these as causes of reduced generation and whether they will propose measures when necessary. If shadows or soiling are found on site, the practical value differs depending on whether the contractor only reports them or also proposes improvements.

Responses related to parts and equipment are also important. If a drop in power generation is related to equipment failure, it may be necessary to verify warranties, arrange repairs, handle replacements, and investigate the cause. Within the O&M contract, confirm whether tasks such as checking warranty documents and supporting contact with relevant parties are included, or whether the power producer must handle them. If warranties or insurance are involved, on-site photos, the date and time when the anomaly occurred, inspection records, and alert logs may be required. Confirming how records should be kept before signing the contract will make subsequent procedures easier.

The purpose of checking work outside the contract scope is not to shift blame. It is to enable you to proceed to the next course of action without delay when power output declines. By clarifying what can be done within the contract, what requires separate judgment, and how emergencies are handled, the speed of response after detecting an abnormality will improve. Before entering into an O&M contract, it is important to confirm not only the inspection items but also the operational workflow after an abnormality is detected.

Confirm whether you can receive long-term improvement proposals

To avoid overlooking declines in power generation, it is important not only to carry out daily monitoring and regular inspections but also to receive long-term improvement proposals. Solar power systems do not remain in the same condition they were at start-up. The surrounding environment, equipment condition, wiring, racking, monitoring environment, and management practices change over time. An O&M framework that not only responds to short-term anomalies but also proposes improvements based on generation trends makes it easier to prevent generation losses.

For long-term improvement proposals, it is important to look at annual trends in power generation. If you only monitor monthly generation, gradual declines can be obscured by seasonal variations and weather effects, making them difficult to detect. By comparing data across multiple years and examining the same seasons, similar solar irradiance conditions, and differences between components within the same installation, it becomes easier to spot signs of slow performance degradation or environmental change. Before entering into a contract, make sure there will be not only monthly reports but also annual reviews and opportunities for improvement proposals.

Improvement proposals do not necessarily have to involve large-scale modifications. Measures such as revising the timing of vegetation management, fixing camera positions during inspections, using more granular units for comparing power output, reviewing procedures for checking monitoring alerts, adding items to reports, and strengthening the reconciliation between on-site displays and remote monitoring values can all reduce missed detections of power output declines through operational improvements. Before entering into an O&M contract, it is important to confirm whether the provider can offer not only responses when abnormalities occur but also proposals to make abnormalities less likely to occur.

Especially in facilities where low power generation recurs repeatedly, a one-off repair may not lead to a fundamental improvement. For example, when shading appears at the same time each year, specific spots remain dirty after rain, the same equipment repeatedly experiences communication faults, or the same circuit shows output discrepancies, you need to regard the causes as trends. Whether an O&M company has a system to propose measures based on past reports and data will make a significant difference in long-term operation.

Also, equipment information management is involved in long-term improvement. If drawings, single-line wiring diagrams, equipment lists, warranty documents, inspection records, repair histories, power generation data, and photographic records are not organized, investigations into the cause will be delayed when power output declines. Before signing a contract, confirm how these materials will be managed and how they will be used for inspections and reporting. A system that investigates from scratch each time without reviewing past records risks repeating the same problems.

When comparing O&M contracts, it is important not to judge solely by the number of tasks. What matters is whether there is a process to detect declines in power generation early, investigate the cause, and prevent recurrence. If monitoring, inspections, reporting, follow-up actions, and improvement proposals are connected, O&M becomes not only a way to protect equipment but a management system that supports the profitability of the power generation business.

By confirming even long-term improvement proposals in advance, an O&M contract becomes not merely a maintenance outsourcing but an operational system that makes it easier to detect declines in power output. At the pre-contract stage, confirm how power output will be monitored, from daily surveillance to annual reviews.

Summary

To avoid missing a drop in power generation, it is important to confirm details before entering into an O&M contract. Even if you realize after signing, "I thought they would monitor this far," "I expected immediate contact in case of an anomaly," or "I assumed analysis of the causes of reduced generation was included," the response can end up being delayed. To detect low-generation conditions quickly, you need to organize, before contracting, the scope of checks, decision criteria, communication rules, on-site inspections, report contents, additional measures, and improvement proposals.

What's particularly important is to judge a decline in power generation not by intuition but by both data and on-site conditions. Because power generation changes with the weather and the seasons, you cannot deem something abnormal based solely on a simple increase or decrease. By combining solar irradiance conditions, past performance, differences between equipment, alert history, on-site shading and soiling, and communication status, you can more readily approach the cause of low generation.

In an O&M contract, check not only whether monitoring and inspections are included but also whether they are structured to enable early detection of declines in power generation. It is important to verify whether the frequency of reviewing monitoring data is sufficient, whether initial notifications in the event of anomalies are clear, whether on-site inspections are reconciled with generation data, whether causes can be traced in reports, whether responses outside the contract scope will not be discontinued, and whether there are long-term improvement proposals.

If a low power generation condition is left unaddressed, generation losses can accumulate, and investigating the causes and restoring operation may take time. On the other hand, by understanding the key points to check before signing a contract, you can detect signs of anomalies earlier and more readily take the necessary actions. An O&M contract should not be viewed merely as a request for inspections; it is important to consider it as a mechanism for continuously protecting power generation.

If you want to establish a management system that does not overlook declines in power generation, consider a mechanism that integrates on-site condition recording, verification of generation data, and organization of inspection histories. Before contracting, it is important to specify the roles of the O&M company and your own company and to put in place operational procedures that allow you to quickly detect low-generation conditions.