How to Check Your Solar Panels Without Taking Them Apart
When a solar PV system produces less energy than expected, the first question is often: which part of the system has changed?
Checking a PV system does not always mean dismantling panels, disconnecting strings or immediately carrying out complex electrical measurements. There are simpler ways to begin an investigation.
Your inverter says how much energy you produced — but what next?
Modern solar inverters provide useful information about the energy produced by a PV system.
A homeowner may notice that today's production is lower than yesterday's, or that monthly production appears to have changed compared with previous years.
But a lower kWh figure does not automatically mean that a solar panel has failed.
Solar production changes with weather, sunlight, season, temperature, shading, system operating conditions and many other factors.
A more useful question is: "Did the PV system behave differently under comparable conditions?"
Why testing individual PV modules can be inconvenient
A PV array can contain dozens or even hundreds of modules. Depending on how the installation is configured, the modules may be connected into strings and routed to one or more inverters.
A simple electrical measurement at the wrong point may not tell the whole story.
Access can also be difficult. Rooftop installations may be high above ground, while commercial installations can cover large areas.
In addition, electrical testing can involve hazardous DC voltages. Anyone carrying out electrical measurements should have the appropriate competence, equipment and safety procedures.
Different ways of checking a PV system
There are several levels of PV testing. The right method depends on what you are trying to find out.
| Method | Useful for | Limitation |
|---|---|---|
| Inverter monitoring | Monitoring energy production and system operation over time. | A change in kWh does not necessarily identify the cause of the change. |
| Visual inspection | Looking for obvious dirt, shading, physical damage or installation issues. | Many electrical or performance problems are not visible. |
| DC electrical measurement | Measuring current or voltage where appropriate. | Requires suitable electrical equipment, access and safety procedures. |
| Irradiance-based comparison | Comparing PV performance observations with the sunlight available at the test location. | Measurements need suitable sensor positioning and reasonably stable, comparable conditions. |
Why measure irradiance?
Irradiance is a measure of solar radiation arriving at a surface and is commonly expressed in watts per square metre (W/m²).
It provides useful context for understanding PV output.
If the available sunlight is changing rapidly, comparing two PV measurements can become difficult because the conditions themselves are changing.
Conversely, when the sunlight is reasonably stable and the sensor is positioned consistently, irradiance can provide a practical reference for repeat measurements.
The PVBuddy approach: establish a reference first
PVBuddy takes a practical comparative approach.
Instead of claiming that every user needs a laboratory irradiance measurement, the PVS01 sensor can be tuned to an existing reference appropriate to the user's purpose.
Flexi-Cal™
In the inverter-reference approach, the sensor is tuned using the inverter kWh reading for a representative string or strings having the same orientation.
Where the user has an appropriate calibrated irradiance meter, the PVS01 can instead be tuned against that reference.
The resulting reference can then be used for subsequent comparative checks.
A simple way to perform a comparative check
The objective is not to make a complicated diagnosis in one measurement. The objective is first to establish a useful reference and then look for a repeatable change.
Select the test area
Select the module, string or group of strings to be checked. Place the PVS01 sensor in the same orientation as the PV area being assessed.
Establish your reference
Check the inverter kWh reading and tune the PVS01 sensor using the PVBuddy App for that string or strings having the same orientation.
Repeat the test
Return to the same test area and position the sensor consistently under comparable and stable sunlight conditions.
Compare the result
Compare the new measurement with the established reference. A repeatable deviation can provide a reason to investigate the PV area further.
What if you find a difference?
A difference is a reason to investigate — not automatically proof that a particular panel or component has failed.
There are many possible causes of a change in PV performance.
Shading
Trees, buildings, new structures or other objects may affect sunlight reaching part of an array.
Soiling
Dust, dirt, leaves or other deposits can reduce the sunlight reaching the module surface.
Electrical issues
Connections, cabling, inverter operation or other electrical conditions may require further investigation.
Module condition
Ageing, physical damage or other module-related conditions may affect performance.
Weather
Cloud, haze and rapidly changing sunlight can affect measurements and should be considered before drawing conclusions.
Measurement conditions
Sensor orientation, position and changing sunlight can affect the usefulness of a comparison.
From one module to an entire PV system
One advantage of a comparative approach is that the same basic principle can be applied at different levels.
- A single module can be assessed as an individual test area.
- A PV string can be used as a reference or test area.
- Several strings with the same orientation can be compared using a common reference.
- Different orientations can be assessed separately by establishing the appropriate reference for each area.
This makes the method particularly interesting for PV owners who want to move beyond simply watching the total kWh number on their inverter.
A useful idea beyond rooftop solar
Comparative irradiance-based checking can also be useful when evaluating individual PV modules outside their original installation.
For example, someone involved in PV module reuse or recycling may want to determine whether a discarded module is worth further evaluation.
The purpose is not to replace formal module testing or certification. Rather, a quick comparative assessment can help decide which items deserve more detailed examination.
Who might find this useful?
- Homeowners with an existing solar PV installation.
- DIY enthusiasts who want to understand their PV system better.
- PV technicians carrying out preliminary field checks.
- Users evaluating individual or groups of PV modules.
- PV module reuse and recycling projects.
- Schools and training centres demonstrating practical solar measurement.
A practical check is not the same as formal PV certification
It is important to understand the difference between a practical field comparison and formal testing.
Professional PV laboratories and qualified testing organisations may use calibrated instruments, controlled procedures and specialised equipment depending on the purpose of the test.
PVBuddy is intended for practical comparative field assessment. It should not be represented as a replacement for formal certification, traceable laboratory measurement or specialist testing where those are required.
establish a useful reference, repeat the measurement consistently, and identify changes worth investigating.
You don't always need to take the PV system apart to start looking for a change
Solar PV systems are designed to operate for many years. That makes it useful to have a practical way of checking whether a system continues to behave consistently.
Inverter monitoring tells you about energy production. Visual inspection can reveal obvious physical conditions. Electrical testing can provide more detailed information when carried out correctly.
Irradiance-based comparative checking adds another piece to the picture by considering the sunlight available at the test area.
PVBuddy PVS01 brings these ideas together into a compact field tool designed to establish a practical reference and help identify repeatable changes.
Ready to check your PV system?
See how PVBuddy PVS01 uses the Flexi-Cal™ approach for practical comparative PV checking.
View PVS01Related reading
Learn why irradiance is important when comparing PV measurements in: Solar Irradiance: The Missing Number When Checking Your PV System .
You may also find our PV Solar System Checklist useful as a reminder for routine system observations.
