Solar panels must withstand years of mechanical stress from wind pressure, snow accumulation, and their own weight. The IEC 61215 MQT 16 static mechanical load test verifies that a module can endure the minimum design loads it will face in the field without structural or electrical failure. Here is a complete breakdown of what the test involves.
What is the MQT 16 Static Mechanical Load Test?
MQT 16, defined in IEC 61215-2:2021, assesses the structural integrity of a photovoltaic module under sustained static loading. Its purpose is:
To determine the ability of the module to withstand a minimum static load.
MQT 16 verifies minimum test loads. The manufacturer's minimum design load is back calculated from the above minimum test load. The test load is defined as:
Test load = γm × design load
where the safety factor γm is at least 1.5.
The minimum required design load per this standard is 1 600 Pa, resulting in a minimum test load of 2 400 Pa. The manufacturer may specify higher design loads for positive (downward) and negative (upward) loading, and also a higher γm for certain applications. The design load(s) and γm must be specified in the manufacturer's documentation for each mounting method.
Example: A manufacturer specifies design loads of positive 3 600 Pa and negative 2 400 Pa with γm = 1.5. The test sequence will contain 3 cycles each performed at 5 400 Pa positive and 3 600 Pa negative loading.
Each module undergoing MQT 16 must be pre-tested according to Sequence E before the load test is applied.
Note: Inhomogeneous snow loads are not covered by this test.
Required Apparatus
The following equipment is required:
• A rigid test base which enables the modules to be mounted front side up or front side down. The test base shall enable the module to deflect freely during load application within the constraints of the manufacturer's prescribed method of mounting.
• Instrumentation to monitor the electrical continuity of the module during the test.
• Suitable weights or pressure means that enable the load to be applied in a gradual, uniform manner. The load may be applied pneumatically or by means of weights. All force shall be applied normal to the module surface. The apparatus shall not contribute to the rigidity of the module (e.g. force applied via a large, flat plate).
• The entire payload shall be applied to the module surface uniformly and gradually without causing impact spikes. The weight shall only be applied on the front sheet (e.g. the glass) and not on the module frame or cross support rails.
• If an automated system using pistons is used to load the module, document the coverage ratio in the test report. Coverage ratio is the area under the suction cups connected to pistons relative to the surface area of the module. A minimum coverage ratio of 10% is recommended to assure uniformity of loading.
Environmental conditions for performing the tests are (25 ± 5) °C in a relative humidity not exceeding 75%.
Note: As most adhesives will perform worse under elevated temperatures, room temperature is considered to be a best case condition for testing.
Test Procedure
Step 1 — Set up electrical monitoring
Equip the module so that the electrical continuity of the internal circuit can be monitored continuously during the test.
Step 2 — Mount the module
Mount the module on a rigid structure using the method prescribed by the manufacturer, including the mounting means (clips/clamps and any kind of fastener) and underlying support rails. Where different mounting possibilities exist, each configuration must be evaluated separately. Mount the module in the configuration where the loading is worst case — this is typically associated with the largest cantilever (overhang span) or largest deflection. For all mounting configurations, mount the module so that the distance between the fixing points is worst case, which typically results in the worst deflection of the module, while following manufacturer recommendations for the specified mounting means.
Allow the modules to equilibrate for a minimum of 2 hours after MQT 13 before applying the load.
For flexible modules, mount according to the manufacturer's documentation with prescribed substrate and adhesive or attachment means during the test.
Step 3 — Apply load to the front surface
On the front surface, gradually and uniformly apply the test load. Load uniformity must be better than ±5% across the module with respect to the test load. Maintain this load for 1 hour.
Step 4 — Apply load to the back surface
Apply the same procedure to the back surface of the module, or as uplift load to the front surface.
Step 5 — Repeat
Repeat steps 3 and 4 for a total of three cycles.
Final Measurements
After completing all three cycles, repeat the following measurements:
• MQT 01 — Visual inspection
• MQT 15 — Wet leakage current test
Pass/Fail Criteria
A module passes MQT 16 if it meets all three of the following requirements:
1. No intermittent open-circuit fault detected during the test.
2. No evidence of major visual defects, as defined in IEC 61215-1:2021.
3. Wet leakage current must meet the same requirements as for the initial measurements.
Why MQT 16 Matters for PV Module Certification
Wind uplift and snow loading are among the leading causes of structural failure in solar installations. A module that passes MQT 16 has demonstrated it can sustain the minimum design loads set by the standard without delaminating, cracking, or losing electrical continuity, critical for installations in regions with high wind speeds, heavy snowfall, or demanding roof-mount configurations.
The test is particularly relevant for projects where local building codes require modules to meet specific structural load ratings, or where the mounting configuration places greater mechanical demands on the module than standard ground-mount systems. Together with MQT 17 (hail impact) and the environmental stress tests, MQT 16 forms part of the complete structural and environmental qualification picture that ensures long-term field reliability.
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Source: IEC 61215-2:2021 — Terrestrial photovoltaic (PV) modules – Design qualification and type approval – Part 2: Test procedures, Section 4.16