Is Your Factory Solar System Underperforming?

Primary sources reviewed: 15 October 2026. This guide addresses operating factory rooftop solar systems in Peninsular Malaysia.

A factory solar system may be underperforming when measured output remains below a credible expectation after weather, data quality and operating conditions have been considered. A low reading on one afternoon, a blank monitoring screen or a smaller bill saving does not establish the cause. Start by confirming what was measured, over which period and against which baseline.

The aim is to prepare evidence for a professional review. This article does not diagnose equipment faults or provide instructions for electrical repairs.

What does your monitoring figure actually measure?

Confirm whether the display shows solar generation, grid imports, exports or consumption at the facility. Note the units and time period. Power in kilowatts (kW) is a rate at a particular time; energy in kilowatt-hours (kWh) is an amount accumulated over a period. They should not be compared as though they were the same measurement.

Check whether all inverters are represented and whether the displayed records are current. Keep the original export or screenshot with its date, time and equipment label. A missing communication link can leave a gap in the dashboard without proving that generation stopped.

Ask the monitoring provider to explain any differences between the dashboard, inverter records and available metering. The first task is to establish a reliable dataset, rather than choose a fault explanation from a single graph.

How should actual generation be compared with expected output?

Ask the assessor to identify the baseline and its limitations. Possible approaches include a project-specific generation model, a suitable historical period or comparison with comparable parts of the installation. Differences in equipment, orientation, shading and operating conditions need to be considered before treating two datasets as comparable.

IEA PVPS’s review of PV failure monitoring describes approaches including comparison with historical output, predicted output and other systems or subsystems. It also notes differences in monitoring data availability and accuracy. These approaches support an investigation; none makes every dashboard comparison conclusive.

Ask what environmental data and design assumptions support the expected figure. An annual generation estimate should not be divided into identical daily targets and treated as a fault threshold. Keep the original forecast and record any later system or site changes.

Is lower generation caused by weather or a system problem?

IEA PVPS’s analytical monitoring guidance discusses measurement quality, temperature effects, shading, inverter sizing and analysis of system losses. This is a reason to review the conditions behind a change, rather than infer equipment failure from a fall in output alone.

Ask for a comparison over a suitable period using the available solar-resource and temperature information. A historical month can be useful context, but it is not automatically a weather-adjusted benchmark. If the difference persists, ask the assessor to document the evidence and identify what further checks would distinguish the possible causes.

There is no universal percentage shortfall in this guide that establishes a fault at every factory. Any contractual performance guarantee should be assessed using the measurement method and conditions defined in that agreement.

What patterns are worth reporting?

The following observations help frame questions for the service team. They are not diagnoses.

Can shutdowns or export controls reduce factory solar output?

Share production schedules, holidays, maintenance outages and changes in electricity demand with the assessor. Ask how the system is intended to behave during low-load periods, and whether the control logs explain what occurred.

For grid-connected SELCO, section 3.4 of the Energy Commission’s June 2026 guidelines prohibits power evacuation to the utility system. Where generation is limited to meet that requirement, reduced output may reflect the operating constraint rather than an equipment defect. Have the responsible engineer confirm the actual configuration; do not change export-control settings to test an assumption.

Our ATAP vs SELCO guide explains the programme distinction. The approved connection arrangement and installed controls need checking for the individual factory.

Does low output mean the panels need cleaning?

Cleaning is one possible consideration, not an automatic remedy. IEA PVPS’s soiling fact sheet identifies dust, pollution and biological debris as sources of loss and discusses measurement and site-specific mitigation.

Tell the team about nearby construction, new shading, industrial emissions or changes since commissioning. Ask how they will assess the likely cause and whether cleaning or another investigation is justified. Do not replace site evidence with a global average loss figure or a fixed cleaning interval.

Any roof inspection or cleaning should be planned through the service team. Factory staff should not climb onto the roof or open electrical equipment to collect evidence for an enquiry.

Why can savings fall even if generation looks normal?

Generation performance and financial performance are related, but they are different questions. Compare electricity use, on-site solar consumption, eligible exports, tariffs and ongoing expenses for the same period.

For example, a production change can alter how much generated electricity is used at the factory without demonstrating an equipment failure. Ask for a bill-based explanation alongside the generation review. Our industrial solar payback guide explains why generation alone is not enough to establish savings.

What should you send for a performance investigation?

Provide the facility location, installed panel and inverter capacities, commissioning date and equipment details. Include the original generation forecast, available monitoring exports, alarm history, recent service records and the date the concern first appeared. Share electricity bills, operating schedules and known grid or factory outages where available.

Identify any changes to the roof, equipment, monitoring platform or production process. Keep the records in their original form and state which periods contain missing data. Ask the service team which additional records are needed before arranging specialist access or testing.

What should the investigation report explain?

Request a clear statement of the dataset, baseline, assumptions, limitations and findings. The report should distinguish confirmed issues from possible explanations and identify any further work requiring approval.

If corrective work is proposed, agree the scope, cost responsibilities and how the outcome will be checked. A follow-up assessment should use a suitable comparison basis, rather than claiming success from one sunnier day after a visit.

Contact Candela about monitoring and maintenance with your system details and records. Our factory solar maintenance guide explains how to agree monitoring responsibilities, investigation approvals and service reporting. Confirm the assessment scope and equipment compatibility with the team; this article does not promise a diagnosis, response time or recovered generation figure.