Can Hail Damage Solar Panels? New 35 mm Hail-Resistant Modules Explained

New n-type glass-to-glass solar modules have been qualified for 35 mm hail impacts. Here is what hail resistance really means, how panels are tested, and what solar owners should know.

News report · August 19, 2026 · 9 min read

Solar panels spend decades outdoors, where they must survive heat, rain, wind, humidity, temperature cycling—and sometimes hail.

That makes a recent product launch from Indian manufacturer Kosol Energie especially interesting. In August 2026, the company introduced enhanced n-type TOPCon glass-to-glass solar modules that it says have been qualified for 35 mm hail impact testing.

The company's announcement matters because the commonly referenced baseline hail test under IEC 61215 uses a 25 mm ice ball traveling at 23 m/s. The U.S. Department of Energy notes that this minimum certification test does not necessarily represent the most severe hail that a solar installation may experience.

So, can hail actually damage solar panels?

Yes.

Most modern modules are designed and tested to survive ordinary weather exposure, but sufficiently large or fast-moving hail can crack front glass, create hidden cell microcracks, damage electrical interconnections, and reduce long-term reliability.

The more useful question is not whether solar panels are "hail proof."

It is:

How much hail impact can a particular module withstand, and how should owners interpret hail-resistance claims?

What Did Kosol Energie Announce?

Kosol Energie introduced new n-type TOPCon glass-to-glass PV modules designed for higher resistance to extreme weather.

According to the company information reported by pv magazine India, the modules have been qualified for 35 mm hail impact testing at a NABL-approved IEC laboratory.

The modules are available in several high-power configurations, including:

600 Wp
620 Wp
630 Wp
715 Wp

The company says the products use half-cut M10R, G12R, and G12 cell formats, depending on the configuration.

Kosol also highlights several construction features intended to improve durability, including:

Thermally tempered solar glass
Glass-to-glass construction
POE encapsulation
Anti-reflective coated glass
N-type TOPCon cells

The most important claim for hail resistance, however, is the 35 mm impact qualification.

A strong-looking module does not automatically prove hail performance. A measured impact test is far more useful than appearance alone.

How Big Is 35 mm Hail?

A diameter of 35 mm is approximately:

35 mm ÷ 25.4 = 1.38 inches

So the test uses ice balls roughly 1.4 inches in diameter.

For comparison, the baseline 25 mm hail-ball size is approximately:

25 mm ÷ 25.4 = 0.98 inches

or about one inch.

The difference may look small when measured only by diameter, but impact severity does not increase linearly with diameter.

A larger hailstone has much more mass.

The U.S. Department of Energy summarizes optional IEC hail-test levels with the following approximate values:

Ice Ball Diameter	Mass	Test Velocity
25 mm	7.54 g	23.0 m/s
35 mm	20.7 g	27.2 m/s
45 mm	43.9 g	30.7 m/s
55 mm	80.2 g	33.9 m/s
65 mm	132 g	36.7 m/s
76 mm	203 g	39.5 m/s

The 35 mm test therefore represents a substantially more energetic impact than the minimum 25 mm test.

Why Bigger Hail Is Much More Destructive

Impact energy depends strongly on both mass and velocity.

A simplified kinetic-energy equation is:

E = ½mv²

where:

E = kinetic energy
m = mass
v = velocity

Using the DOE's listed test values:

25 mm hail ball

Mass:

7.54 g = 0.00754 kg

Velocity:

23 m/s

Approximate impact energy:

E = ½ × 0.00754 × 23²

E ≈ 1.99 joules

35 mm hail ball

Mass:

20.7 g = 0.0207 kg

Velocity:

27.2 m/s

Approximate impact energy:

E = ½ × 0.0207 × 27.2²

E ≈ 7.66 joules

That is nearly:

7.66 ÷ 1.99 ≈ 3.85

or roughly 3.8 times the kinetic energy in this simplified comparison.

This is why a modest-looking increase in hail diameter can create a much more demanding impact.

What Is the IEC 61215 Hail Test?

IEC 61215 is part of the international qualification framework used for terrestrial photovoltaic modules.

Among many reliability tests, the standard includes hail-impact testing.

The U.S. Department of Energy describes the basic hail certification test as involving 25 mm ice balls at approximately 23 m/s, or about 51 mph.

Modules are struck at multiple locations.

According to DOE guidance, the module must remain visually acceptable and maintain power within the permitted degradation limit after the required impacts.

However, DOE makes an important point:

Passing the basic hail test does not mean a module cannot be damaged by severe or very severe real-world hail.

The minimum qualification test is a baseline.

Larger hail sizes can be tested at higher velocities, and independent reliability laboratories also offer more demanding hail sequences.

Does "Hail Certified" Mean Hail Proof?

No.

This is one of the most important distinctions for homeowners.

A module can pass the required certification test and still be damaged by a storm that exceeds the conditions used during qualification.

Think of the test as evidence that the panel can withstand a defined impact level.

It is not a guarantee against every possible hailstorm.

Real hail events can vary by:

Stone diameter
Stone shape
Density
Wind speed
Impact angle
Number of impacts
Repeated strikes at similar locations
Existing glass or cell damage
Module orientation
Module support conditions

A severe storm may therefore expose a panel to stresses substantially beyond the basic test.

Can Hail Break Solar Panel Glass?

Yes.

The most visible form of hail damage is cracked or shattered front glass.

Solar modules normally use heat-treated or tempered glass designed for strength and optical transmission.

But no glass is infinitely strong.

A sufficiently energetic impact can initiate a crack.

Once the glass surface is damaged, several additional problems may follow:

Moisture can enter the module
Electrical insulation can be compromised
Cell protection is reduced
Cracks may propagate
Long-term degradation can accelerate

A panel with obviously shattered glass should not simply remain connected because it still produces power.

It needs inspection and appropriate electrical safety handling.

Hail Damage Can Be Invisible

The front glass does not have to shatter for hail to damage a solar module.

The silicon cells inside the panel are thin and brittle.

An impact can create microcracks in the cells while the external glass still looks normal.

Microcracks matter because they may:

Disconnect part of a cell
Increase electrical resistance
Reduce current-producing area
Create inactive regions
Contribute to future hotspot risk
Grow under repeated thermal and mechanical stress

This is why visual inspection alone may not detect every form of hail damage.

How Can Hidden Cell Cracks Be Detected?

Solar manufacturers and testing laboratories can use electroluminescence imaging, often abbreviated EL.

During EL testing, electrical current is driven through the solar cells.

The cells emit faint infrared light that can be captured by specialized cameras.

Cracks and electrically inactive regions can appear as abnormal dark patterns.

Other useful diagnostic methods can include:

I-V curve testing
Infrared thermography
Insulation testing
Visual inspection
String-level monitoring
Module-level power comparison

After a severe hailstorm, a professional inspection may therefore involve more than simply checking whether the glass is broken.

What Happened at NREL During a Real Hailstorm?

A famous real-world example comes from the National Renewable Energy Laboratory campus in Colorado.

In May 2017, a severe hailstorm struck the area.

According to the U.S. Department of Energy, only one panel out of more than 3,000 in the affected installation was found with broken glass after the storm.

The damaged module appeared to have received many impacts concentrated around an already damaged region.

The event showed that modern modules can be surprisingly resilient.

However, it should not be interpreted as proof that every solar panel will survive every hail event.

Panel design, hail size, angle, wind conditions, installation geometry, and storm severity can all be different.

Why Does Glass Thickness Matter?

Front glass is the first structural barrier protecting most conventional crystalline-silicon modules from hail.

DOE guidance for hail-prone projects recommends considering modules with at least 3.2 mm front glass, and notes that thicker front glass can improve resistance.

But there is an important nuance.

Many modern bifacial glass-to-glass modules use two sheets of glass and may use different individual glass thicknesses from traditional glass-backsheet modules.

That means you should not judge a panel only from a single specification such as:

"dual glass"

or:

"3.2 mm glass."

The more useful evidence is a combination of:

Actual hail-test result
Glass construction
Frame strength
Module size
Encapsulation
Mechanical-load qualification
Independent reliability testing

A specific tested result is stronger evidence than a marketing label by itself.

What Is a Glass-to-Glass Solar Panel?

A traditional crystalline-silicon module often has:

Front glass
Encapsulant
Solar cells
Encapsulant
Polymer backsheet

A glass-to-glass, or dual-glass, module replaces the polymer backsheet with another glass layer.

A simplified cross-section becomes:

Front glass

Encapsulant

Solar cells

Encapsulant

Rear glass

Glass-to-glass construction can improve environmental sealing and mechanical stability in some designs.

It is also widely used for bifacial modules because the rear glass can allow light to reach the back side of bifacial cells.

However:

Glass-to-glass does not automatically mean hail proof.

The complete module design still has to be tested.

Why Does Encapsulant Matter During Impact?

The encapsulant surrounds and supports the solar cells inside the module.

Common encapsulation materials include:

Kosol says its hail-resistant modules use POE encapsulation intended to provide additional protection against mechanical and environmental stress.

During an impact, the front glass experiences the initial force.

But the mechanical energy can propagate through the module stack.

The encapsulant can influence:

Cell support
Stress distribution
Adhesion
Moisture resistance
Electrical insulation
Long-term crack behavior

That is why hail durability depends on the complete module construction rather than only the outer glass.

Does the Aluminum Frame Help?

Yes, module support conditions can influence mechanical behavior.

DOE guidance recommends considering framed modules and stronger frame construction for hail-prone projects.

The frame helps support the module edges and transfers mechanical loads into the mounting structure.

However, hail commonly strikes the glass surface rather than the frame.

A strong frame therefore cannot compensate for weak glass or cells.

It is one component in the overall structural design.

Are Bigger Solar Panels More Vulnerable?

Potentially.

The U.S. Department of Energy notes that larger-format modules may face higher hail-damage risk than smaller modules in some circumstances.

A larger glass surface can flex differently under mechanical impact and has a greater exposed area.

Modern utility modules can also be physically very large.

That does not mean large modules are unsafe.

It means manufacturers and project designers should make sure reliability testing keeps pace with increasing panel dimensions.

A 700 W module should not be evaluated only by its impressive power rating.

Mechanical durability matters too.

Why Solar Panel Wattage Tells You Almost Nothing About Hail Resistance

Consider two hypothetical panels:

Panel A

450 W
22.5% efficiency
Standard hail qualification

Panel B

450 W
22.5% efficiency
Enhanced hail qualification

Electrically, the two modules may look similar.

Mechanically, they may perform very differently during extreme weather.

Hail resistance depends on details such as:

Front glass
Cell architecture
Encapsulant
Frame
Module dimensions
Mechanical support
Manufacturing quality
Test level

This is an example of why choosing a solar panel based only on wattage or efficiency can miss important reliability factors.

What Is N-Type TOPCon?

Kosol's new modules use n-type TOPCon solar cells.

TOPCon stands for tunnel oxide passivated contact.

It is an advanced crystalline-silicon cell architecture designed to reduce electrical recombination losses and improve conversion efficiency.

The "n-type" description relates to the silicon wafer and its doping characteristics.

TOPCon has become widely used in newer high-efficiency modules.

However, n-type TOPCon itself is not what makes a panel hail resistant.

Cell technology primarily concerns photovoltaic conversion.

Hail durability depends mainly on the complete mechanical module structure and qualification testing.

A manufacturer can combine high-efficiency TOPCon cells with a mechanically reinforced module design, but those are different engineering goals.

What Does 600 Wp or 715 Wp Mean?

The Wp rating means watt-peak.

It represents the module's rated maximum power under specified standard test conditions.

For example:

715 Wp = 715 watts of rated peak DC power under the defined laboratory conditions

It does not mean the panel continuously produces 715 W outdoors.

Actual output depends on:

Solar irradiance
Cell temperature
Angle of sunlight
Shading
Dirt
Wiring
Inverter or controller operation
System losses

Hail resistance also has no direct relationship to Wp.

A 715 W module is not automatically stronger or weaker than a 450 W module simply because its power rating is higher.

Why Extreme Weather Is Becoming Part of Solar Panel Selection

For many years, solar-module buying decisions focused heavily on:

Price per watt
Efficiency
Warranty
Brand
Power rating

Those are still important.

But project developers are paying increasing attention to climate-specific reliability.

A solar panel may operate for 25 years or more.

During that period, a project can experience:

Hail
Hurricanes
Strong winds
Flooding
High humidity
Heat waves
Snow loading
Wildfire conditions
Salt mist in coastal locations

A module that has slightly lower efficiency but substantially better resilience may be more valuable for a high-risk site.

The correct product therefore depends on the environment.

What Should Homeowners Check Before Buying Solar Panels?

If hail is a meaningful risk where you live, ask the installer or module supplier for more than the statement:

"These panels are hail resistant."

Useful questions include:

What hail-test standard did the module pass?
What ice-ball diameter was used?
What impact velocity was used?
Was testing performed by an independent laboratory?
Is the result the minimum IEC requirement or an enhanced test?
What is the front-glass construction?
What does the product warranty say about weather damage?
Does the homeowner's insurance cover hail damage to rooftop solar?
Has the exact module model been tested, or only a related product family?
Are there post-storm inspection procedures?

Those questions produce much more useful information than a simple "hail certified" label.

Does a Solar Panel Warranty Cover Hail?

Not necessarily.

Solar-panel warranties and insurance are different things.

A manufacturer's product warranty generally covers specified defects and failures according to the warranty terms.

Damage caused by extreme external events may be treated differently.

Home or property insurance may cover some weather-related solar damage, depending on:

Policy
Country
Insurer
Installation type
Cause of damage
Exclusions
Deductible

Owners should therefore check the actual warranty and insurance documentation rather than assuming hail damage is automatically covered.

What Should You Do After a Hailstorm?

If a severe hailstorm hits a solar installation, start with safety.

Do not climb onto a wet or damaged roof simply to inspect the panels.

A damaged solar module can still generate DC voltage whenever light reaches its cells.

From a safe location, look for obvious signs such as:

Broken glass
Loose modules
Bent frames
Damaged wiring
Detached connectors
Pieces of glass
Visible impact marks

Then compare system monitoring data if available.

Unexpected changes can include:

Lower string current
Reduced array power
New inverter fault messages
Abnormal MPPT behavior
One string producing less than similar strings

A qualified solar technician can perform a closer inspection and electrical testing.

Can a Cracked Solar Panel Still Produce Power?

Yes.

A damaged module may continue producing electricity.

That does not mean it is safe or healthy.

A cracked panel can have:

Compromised insulation
Moisture ingress
Exposed conductors
Cell cracks
Hotspots
Ground faults
Arc-fault risk
Accelerated degradation

Continuing to generate power should never be used as the only test of whether a damaged panel is acceptable.

Can You Protect Existing Solar Panels From Hail?

There is no universal retrofit that makes every rooftop module immune to severe hail.

For utility-scale systems using solar trackers, one strategy is hail stow.

DOE notes that some tracker systems can rotate modules toward a steep protective angle when severe hail is predicted.

Changing the orientation can reduce the effective impact angle of many hailstones.

For fixed rooftop systems, the options are more limited.

Protective covers might seem attractive, but they create practical problems involving:

Wind loading
Shading
Mounting
Heat
Installation safety
Rapid deployment before a storm

A poorly designed protective cover could create a new hazard.

For most permanent systems, selecting resilient modules and following sound structural design from the beginning is more practical.

Is a 35 mm Hail Qualification Good?

It is meaningfully more demanding than the 25 mm baseline test.

Using the DOE's hail-test table, the 35 mm ice ball is not only larger but also tested at a higher velocity.

That increases impact energy substantially.

However, 35 mm qualification should still be interpreted correctly.

It means:

the module was tested under a defined 35 mm hail-impact procedure

It does not mean:

the module can survive every real storm containing 35 mm hail without any possible damage

Real weather is less controlled than a laboratory.

Impact angle, wind, repeated strikes, existing damage, and unusual hail shapes can change the result.

Why Enhanced Hail Testing Is Useful

Even with those limitations, enhanced testing can help buyers distinguish between products.

Suppose two panels both satisfy the basic qualification standard.

If one manufacturer also provides independent results showing successful performance at:

35 mm
45 mm
or another advanced hail sequence

that additional result provides more information about mechanical resilience.

DOE specifically recommends requesting evidence of testing above minimum IEC requirements for installations in areas exposed to severe or very severe hail.

That is a better approach than assuming all IEC-qualified modules have identical hail performance.

Explore Solar Panel Behavior in PVAlign

Hail resistance is a mechanical property, but hail damage can eventually become an electrical problem when cells or interconnections are affected.

With the PVAlign Solar Power Simulator, you can explore how changes to panel electrical behavior affect a complete solar system.

For example, try comparing what happens when a module or PV branch has:

Reduced current
Lower available power
Partial shading
Mismatched operating conditions
Series-connected neighbors
Parallel-connected neighbors

A damaged or strongly mismatched panel can influence other components differently depending on the array topology.

Simulation cannot replace physical damage inspection, but it can help students understand why one weak section may influence an entire string.

Frequently Asked Questions

Can hail damage solar panels?

Yes. Large or high-energy hail can crack module glass, create hidden solar-cell microcracks, damage interconnections, and reduce long-term performance.

Are solar panels hail proof?

No solar panel should be assumed to be completely hail proof. Panels are tested to defined impact levels, but real storms can exceed those test conditions.

What size hail are solar panels tested against?

The baseline IEC qualification test commonly referenced by the U.S. Department of Energy uses 25 mm ice balls traveling at 23 m/s. Larger optional hail tests can use greater diameters and higher velocities.

What is special about Kosol's new hail-resistant modules?

Kosol says its new n-type TOPCon glass-to-glass modules have been qualified for 35 mm hail impact testing at a NABL-approved IEC laboratory. This is larger than the 25 mm baseline hail-ball size.

Does glass-to-glass mean a solar panel is hail proof?

No. Glass-to-glass describes the module's construction. Hail resistance depends on the full design and should be evaluated using actual impact-test results.

Can hail damage a panel without breaking the glass?

Yes. Impact can create microcracks in the silicon cells even when the front glass appears intact.

How can hidden hail damage be detected?

Methods can include electroluminescence imaging, I-V curve testing, infrared inspection, insulation testing, system monitoring, and professional visual inspection.

Can a cracked solar panel still work?

Yes, but continued power production does not prove the module is safe. Cracked glass or cells can lead to insulation failure, moisture ingress, hotspots, ground faults, or accelerated degradation.

Should I replace a panel after hail?

Not automatically. The correct decision depends on the type and severity of damage. A qualified technician can inspect and electrically test the module before deciding whether it can remain in service.

Are 35 mm hail-resistant solar panels better?

They provide evidence of performance under a more demanding hail impact than the 25 mm baseline qualification. Whether they are "better" overall still depends on efficiency, reliability, cost, warranty, electrical compatibility, installation requirements, and the site's actual weather risks.

The Bigger Picture

Solar-panel technology is usually discussed in terms of higher efficiency and lower cost.

The new generation of hail-resistant modules highlights another part of solar engineering:

survival.

A module that produces impressive power on its first day is only valuable if it can continue producing safely through years of real weather.

Kosol Energie's reported 35 mm qualification is one example of manufacturers pushing module testing beyond the basic hail size commonly associated with IEC certification.

That does not make the panel indestructible.

Instead, it gives project designers another measurable specification to consider.

For homeowners and solar developers, the key lesson is simple:

Do not ask only how many watts a solar panel produces. Ask what conditions it has been designed and tested to survive.

Efficiency determines how effectively a panel converts sunlight.

Reliability determines whether it can keep doing that for decades.

A high-quality solar project needs both.