The short answer
When one panel looks weaker in a solar-monitoring app, first check whether its data is current and whether you are comparing similar panels over the same period. Save the device identifier, full-day energy totals, and the date the pattern began. A qualified solar technician should distinguish a reporting problem, a site condition, and an equipment fault before recommending a panel or microinverter replacement.
A darker square in an array diagram is a starting observation. It does not identify the failed part. This guide is for systems with panel-level monitoring and a persistent concern about one module position. If your app shows only total-system production, ask the service provider what device-level evidence is available; do not assume it can identify an individual panel from a household electric bill.
Keep the investigation in the app and at a safe ground-level viewing point. Do not climb onto the roof, cover a panel to test the map, disconnect connectors, swap equipment, or open an electrical enclosure. For smoke, fire, arcing, or another immediate threat, move away and contact emergency services. For observed damage without an active emergency, keep away from the affected equipment and contact qualified solar or electrical service.
Confirm that the displayed number is the number you mean
Check the screen's units and date range before describing the loss. Watts or kilowatts describe power at a particular moment; watt-hours or kilowatt-hours describe energy over a period. The U.S. Energy Information Administration explains this distinction. A morning power snapshot and a completed day's energy total answer different questions. EIA measuring electricity
Record the suspect device's daily energy and the daily energy of a few comparable devices using the same dates and units. Include the last-reporting time and any alert. If the app offers a power trace, save that as additional evidence rather than substituting it for the daily comparison.
For an Enphase system, a Microinverter Not Reporting alert concerns data reaching the gateway and does not always establish a production failure. Enphase recommends checking when the affected device last reported. That matters before treating a low or blank value as measured lost generation. Enphase troubleshooting and support
Ask support whether the values are complete for the selected dates. If they are stale or incomplete, resolve the reporting question first and retain the original screenshots. A fresh stream of data may still reveal an equipment problem, but it gives the technician a firmer basis for that investigation.
Choose peers that make the comparison meaningful
Start with the installation layout and equipment schedule. Ask the installer which modules have the same model, orientation, tilt, and associated inverter or optimizer configuration. The nearest square on the screen is not automatically the best comparison.
DOE's explanation of PV modeling identifies module and inverter characteristics, electrical connections, array orientation, shading, and environmental conditions as relevant inputs. It also explains that models have uncertainty. These are reasons to compare site context and history, rather than declare a universal percentage difference a failed-panel threshold. DOE modeling resources for photovoltaic system owners
Use the suspect position's own earlier data as well as its peers. Did it previously track those devices and then change, or has it always followed a different pattern? Ask support whether replacements, device reassignment, missing reporting periods, or changes to the array affect the history you are viewing. A lifetime total is less useful if the devices do not share a comparable reporting history.
Have the technician verify the association between the app's device identifier and the physical module position before arranging targeted roof work. Do not try to prove the mapping by shading a module yourself. Your role is to provide the layout and screenshots; the professional's role is to establish which installed equipment they are diagnosing.
Describe when the difference occurs
Look for a repeatable pattern in the data already available. Do not manipulate the system to create one.
If the difference is limited to part of the day, save the relevant time window and ask the technician to assess shading and other site-specific explanations. From a safe location, note a visible chimney shadow, new vegetation, storm debris, or recent nearby construction. A ground photograph may help place the concern, but it cannot clear the hidden condition of a roof panel.
If the suspect device changed abruptly while comparable devices remained similar, include the first date you can document. Note any storm, roof work, replacement, outage, or service visit around that date without declaring it the cause. “The difference began after roof work” is evidence for investigation; “the roofer broke the panel” is an accusation that the app alone cannot support.
If several devices on the same part of the array change together, say so. That expands the diagnostic question beyond a single panel. If only one device is persistently lower with fresh reporting, ask for a device-specific assessment. These branches help choose the service scope; they do not identify a diode, connector, optimizer, or microinverter fault remotely.
Send evidence that supports a remote first look
A concise service request can read:
“Device [identifier] has lower daily energy than comparable devices [identifiers] on the attached dates. Its last-reporting timestamp is current. The difference began on [date] and appears [throughout the day/in the attached time window]. Please confirm the physical mapping, review available event data, and tell me whether an onsite diagnostic is needed.”
Attach the selected-date screenshots, the full error text, the equipment schedule if available, and a ground-level context photo only if safe. Supply the system's site identifier through the provider's official support route, not a public forum.
Ask what the remote review can establish and what it cannot. If support says the microinverter is reporting normally, ask whether that conclusion also addresses the module's performance. If a module manufacturer is likely to handle a claim, ask which measurements and documents that manufacturer requires before scheduling work.
The point is to avoid paying for a visit that collects the wrong evidence. It is equally important not to delay a safety-related inspection while collecting perfect production screenshots.
Make the repair quote identify the finding
Before approving replacement, request a written diagnosis with the affected device and physical location. The report should distinguish observations, test results, and the technician's conclusion. Ask which alternative explanation was checked and why the proposed component addresses the finding.
Useful quote questions include:
- Is the problem in reported data, the module, its associated electronics, a connection, or another identified part of the system?
- Which professional tests are included, and what result would change the proposed repair?
- Does the manufacturer require pre-approval or a return authorization for warranty service?
- Who pays for diagnostic labor, roof access, shipping, replacement labor, and any return visit?
- Will the proposed replacement be documented as compatible with the existing equipment and installation?
- Who updates the monitoring record if a device is replaced, and how will the completed repair be checked?
These are scope questions, not promises that a product warranty pays every charge. Read the applicable written warranty and ask for a case-specific coverage determination. Do not infer a repair price or remaining panel life from another owner's forum post.
DOE's PV weather-vulnerability guide draws a firm boundary around untrained personnel touching electrical components, even when equipment is presumed de-energized. The inspections and electrical tests in a repair scope belong with appropriately qualified personnel. DOE PV System Owner's Guide
Verify the result using the same comparison
After the repair, retain the diagnostic report, old and new equipment identifiers, warranty decision, and final invoice. Ask the provider to confirm the app layout and reporting are correct. Then review fresh data from the suspect position and the same comparison group under suitable conditions identified by the technician.
A completed work order should explain why the result supports closing the complaint. A new component alone is not a performance report. If the difference remains, reopen the same case with the before-and-after comparison and ask whether the original diagnosis needs revision.
If a professional finds no repairable fault, request the explanation in writing: which site condition or equipment characteristic accounts for the pattern, what evidence supports it, and what future change would warrant another review. This turns “keep an eye on it” into a usable plan.
Keep that report with your installation records. The solar and battery maintenance guide describes the broader monitoring and service file that makes later problems easier to investigate.