Hail Impact Test Standards: IEC 61215-2, ASTM E1038, UL 2218 and EN 13583 Requirements Explained

Hail impact test standards define how products such as photovoltaic modules, roofing systems, glazing and outdoor equipment are evaluated against calibrated ice-ball strikes launched at controlled velocities. This article explains the key hail impact test standards — IEC 61215-2 (MQT 17), ASTM E1038, UL 1703/UL 61730, UL 2218, EN 13583 and the related GB and JIS adoptions — covering sample requirements, testing items, test methods, pass criteria and typical applications. Use this guide to prepare for hail impact testing at accredited third-party laboratories and to streamline product certification.

Technical Overview

A hail impact test is a mechanical robustness test that simulates hailstone strikes on a product by launching calibrated ice balls at defined diameters, masses and velocities against specified target points. The purpose is to verify that outdoor products survive realistic hail events without cracking, penetration, water ingress or unacceptable loss of performance. The test is most closely associated with the photovoltaic (PV) industry, but it is equally important for roofing, waterproofing, automotive glazing and other weather-exposed assemblies.

The fundamental principle is energy control. Each ice ball is characterized by diameter, mass, temperature and impact velocity, and the resulting kinetic energy (E = ½mv²) defines the severity level. Under IEC 61215-2, for example, the default hail test uses a 25 mm ice ball at 23 m/s, delivering approximately 2 J of kinetic energy, while higher severity levels scale up to a 75 mm ball at 52.2 m/s, delivering approximately 276 J. Ice balls are typically conditioned to approximately −40 °C ± 10 °C, and measured velocity must usually be maintained within ±5% of the specified value.

The principal hail impact test standards and their scope include the following:

• IEC 61215-2 (MQT 17, Hail test) — design qualification of terrestrial PV modules; the historical test 10.17 of IEC 61215:2005 and the thin-film standard IEC 61646 have been consolidated into the current IEC 61215-2 series.
• ASTM E1038 — determining the resistance of photovoltaic modules to hail by impact with ice balls.
• UL 1703 and UL 61730 — PV module and panel safety standards that include hail impact requirements aligned with the 25 mm ice ball method.
• UL 2218 — impact resistance of roof covering materials using dropped steel balls, with Class 1 to Class 4 severity ratings (Class 4, the most severe, corresponds to a 2-inch steel ball dropped from approximately 6 m / 20 ft).
• EN 13583 — determination of hail resistance of bitumen, plastic and rubber sheets for roof waterproofing.
• GB/T 9535 and GB/T 18911 — Chinese national standards for crystalline silicon and thin-film terrestrial PV modules, aligned with IEC 61215 and IEC 61646.
• JIS C 8990 and JIS C 8991 — Japanese standards for terrestrial PV module design qualification, mirroring the IEC qualification approach.

Typical ice ball severity levels used across IEC 61215-2 and ASTM E1038 are summarized below:

• 25 mm diameter, 23.0 m/s, approximately 2 J (default severity)
• 35 mm diameter, 27.2 m/s, approximately 8 J
• 45 mm diameter, 32.6 m/s, approximately 23 J
• 55 mm diameter, 39.5 m/s, approximately 63 J
• 65 mm diameter, 45.6 m/s, approximately 137 J
• 75 mm diameter, 52.2 m/s, approximately 276 J

Testing Samples

Photovoltaic Modules

Full-size production PV modules are tested, including glass-backsheet, glass-glass, bifacial and flexible laminates. Samples must be representative of series production, complete with frame, junction box and cables, and are typically tested at laboratory ambient temperature after standard conditioning. The ice ball impacts are directed normal to the front surface, with the module rigidly mounted in the target fixture.

Building-Integrated PV and Glazing Products

Solar roof tiles, curtain-wall laminates, skylights and architectural glazing are frequently tested to IEC 61215-2 MQT 17 or project-specific ice ball energy levels, because these products combine electrical function with a primary weather-barrier role. Additional sealing and watertightness checks are often specified after impact.

Roofing and Waterproofing Materials

Asphalt shingles, clay and concrete tiles, metal roof panels and polymer/bitumen waterproofing membranes are tested under UL 2218 (steel ball impact) or EN 13583 (hail resistance of flexible sheets). Specimens are installed over a representative substrate and deck construction so that the response of the full roof assembly, not just the surface material, is evaluated.

Automotive, Aerospace and Outdoor Equipment

Body panels, windshields and side glazing, camera and sensor covers, mirror housings, radomes, outdoor enclosures and equipment housings are tested to OEM or industry specifications that commonly adopt the ice ball diameter/velocity framework of the PV standards. This allows designers to specify a proven hail energy level appropriate to the service environment.

Testing Items

Depending on the product and standard, hail impact testing evaluates the following items before and after the impacts:

• Visual inspection for major defects: glass breakage, cracks, delamination, bubbles, surface deformation and coating damage.
• Maximum power (Pmax) measurement on PV modules, with a typical pass criterion of no more than 5% degradation relative to the pre-test baseline.
• Insulation resistance and wet leakage current tests to confirm electrical safety after impact.
• Electroluminescence (EL) imaging to reveal hidden cell micro-cracks that are not visible externally.
• Dent depth, permanent deformation and fracture assessment for roofing and automotive panels.
• Watertightness and penetration checks for roofing and waterproofing assemblies after impact.
• Functional verification of sensors, enclosures and sealing systems where applicable.

Testing Methods

The dominant method is the pneumatic ice ball launch technique. The test sequence generally proceeds as follows:

• Ice ball preparation: spheres are molded from distilled or deionized water, free of trapped air bubbles, inspected for cracks, weighed, measured and conditioned in a freezer to the temperature specified by the standard (approximately −40 °C ± 10 °C under IEC 61215-2).
• Apparatus setup: a compressed-air hail cannon with a barrel matched to the ball diameter propels each ice ball; light gates or an equivalent velocity measurement system placed near the target verify that the impact speed is within tolerance (typically ±5%).
• Baseline characterization: visual inspection, I-V curve measurement and EL imaging are performed before impact to establish reference values.
• Impact execution: the sample is impacted at a defined pattern of target points. For PV modules under IEC 61215-2, a fixed set of impact locations — typically 11 positions covering the center, corners, edges and areas near the junction box and mounting points — is used, with a single impact at each location.
• Post-test evaluation: the sample is re-inspected visually, electrically and by EL imaging, and results are compared against the pass criteria of the standard.

For roofing products, UL 2218 applies a simpler dropped steel ball method: steel balls of increasing size are dropped from increasing heights onto the installed specimen, and the product is classified from Class 1 to Class 4 based on the highest level at which no cracking, tearing, rupture or fracture of the covering occurs. EN 13583 similarly uses controlled impacts to classify the hail resistance of flexible waterproofing sheets, with damage and watertightness evaluated after each energy level.

Throughout all methods, traceability is essential: the diameter, mass, temperature and velocity of every projectile are recorded, the mounting angle and impact point layout are documented photographically, and the test report states the standard edition, severity level and complete pass/fail determination.

Applications

Hail impact testing to recognized standards supports a wide range of engineering and commercial objectives:

• Market access and certification of PV modules through IEC 61215-2 type approval, UL 61730 listing and the corresponding GB and JIS national schemes.
• Bankability assessments, where independent verification of hail durability strengthens project due diligence for investors and lenders.
• Insurance classification of roofing products under UL 2218, which is widely referenced by insurers and building codes for impact resistance ratings and premium considerations.
• Construction product compliance in Europe using EN 13583 for roof waterproofing membranes.
• Research and development of front glass, encapsulants, laminates and support structures to optimize weight, cost and reliability.
• Manufacturing quality control, field failure analysis and warranty adjudication in hail-prone regions.
• Design verification of automotive, aerospace and outdoor electronic products against specified hail energy levels.

FAQ

Which standard governs hail impact testing of solar panels?

IEC 61215-2 (test MQT 17) is the primary international standard for PV module hail resistance. ASTM E1038 provides an equivalent ice ball method, and UL 61730 (formerly UL 1703) includes hail requirements within the module safety evaluation. Chinese GB/T 9535 and GB/T 18911 and Japanese JIS C 8990/C 8991 adopt the same qualification approach.

What ice ball size and velocity are used by default?

The default severity is a 25 mm ice ball launched at 23 m/s, equivalent to approximately 2 J of kinetic energy. Higher severity levels use 35 mm to 75 mm balls at velocities from 27.2 m/s to 52.2 m/s, reaching approximately 276 J for the largest size.

What are the pass criteria for a PV module hail test?

The module must show no major visual defects such as broken glass or delamination, must not lose more than 5% of maximum power compared with the pre-test measurement, and must maintain its insulation resistance and wet leakage performance. EL imaging is commonly used to confirm the absence of hidden cell cracks.

How is impact velocity controlled and verified?

Each ice ball is launched by a pneumatic cannon, and its speed is measured immediately before impact using light gates or an equivalent timing system. The measured velocity must fall within the tolerance defined by the standard, typically ±5%, and the mass, diameter and temperature of every ball are recorded for traceability.

How does the steel ball method differ from the ice ball method?

The steel ball method, used in UL 2218 for roofing, drops hard steel spheres from specified heights to produce repeatable impact energy; the product is classified from Class 1 to Class 4 by severity. The ice ball method, used in IEC 61215-2 and ASTM E1038, reproduces the actual density and fragmentation behavior of hailstones and is the reference approach for PV modules and similar products.

Where should hail impact testing be performed?

Testing should be carried out at accredited third-party laboratories operating calibrated hail cannons, environmental conditioning equipment and electrical characterization facilities under an ISO/IEC 17025 quality management system, ensuring that results are accepted for certification, listing and regulatory purposes worldwide.