Can solar panels withstand hail?

Did you know that the record for a hailstone in the United States is 8 inches? According to CNN, a giant hailstone discovered in South Dakota was the size of a volleyball and weighed almost two pounds. Yikes!

If an 8 inch hailstone hit your solar array, there definitely would be damage. Luckily, hail like this is extremely rare. But what about more ordinary hail?

Solar panels are designed and tested to withstand hail that is rated up to “severe” by the US National Weather Service, which is hail up to one inch in size or with wind gusts up to 58 mph. Hail smaller than this or moving at a slower velocity shouldn’t cause any damage to your solar array.

However, very severe hail - that is, hailstones larger than one inch or accompanied by very strong winds - can damage solar panels by shattering the front side glass panel. While not very common, it does happen, as was the case with this solar farm nean San Antonio, Texas:

If you live in parts of the US Midwest where hail storms are most common, there are a couple measures you might take before installing solar panels on your home, such as buying solar panels with stronger front side glass and checking or updating your insurance policy.

How big a risk is hail damage for solar panel owners?

The greatest risk of severe hail is in the area known as “hail alley” - approximately Texas, Oklahoma, Colorado, Kansas, Nebraska and Wyoming. These are states where severe hail is a risk on multiple days in a year. The US Storm Prediction Center has a map that summarizes the risk:

In this map, you can see that parts of Kansas experience more than a dozen severe hail days a year, on average, with Oklahoma and Nebraska a close second. Severe hail is a smaller risk but still possible throughout much of the eastern half the country, including Texas, which has a significant and growing solar industry.

If you live in one of these places, it might be worth taking measures to reduce your risk of financial losses due to hail-related solar panel damage.

The largest number of home solar panel owners in the US live in California, the Southwest, and parts of the Northeast. While hail is still possible there, it’s much less of a risk. Even so, it may be worth checking on your insurance policy, just in case. More about that later.

How strong are solar panels when it comes to hail?

In the US, solar panels that are connected to the electric grid, such as the solar panels on your roof, must be certified by the California Energy Commission (CEC).

As part of that certification, there are several tests that a solar panel must pass. One of these is IEC 61215, which involves accelerated stress tests to see how well the module holds up under heat, cold, wind, humidity, UV light, and mechnical stress - including hail.

There are two versions of the standard: the original IEC 61215, and a newer IEC 61215:2005. There is a difference in strength rating between the two tests - read more about that later.

The hail test basically involves shooting 25 mm (one inch) ice pellets at 23 meters/second (51 miles per hour) at the panel. If the panel survives 11 such impacts, it passes the test.

According to the National Oceanic & Atmospheric Administration (NOAA), one inch hail is considered severe, and hailstones in a severe thunderstorm would be expected to fall at about 40 mph at most. So, this test exceeds the velocity of hail impacts even in a severe thunderstorm.

Here’s a video of what that solar panel hail testing looks like. Be aware that the last two projectiles that shatter the glass are plastic and steel balls, not ice.

Checking solar panel strength ratings

It’s a good idea to take a look at the datasheet for the solar panels you intend to install on your home. While the specs can appear complicated, there’s only a few key things to look out for. I wrote a post to help you deciper them.

One of these key things is the strength rating of the panel. There will be two ratings.

The frontside strength, also called the snow load rating, tells you how much force the front of the panel is designed to withstand.

The backside strength, also called the wind load rating, measures the strength of the rear of the panel.

They’re labelled this way because the weight of snow will land on the front side of the panel, while ground-mounted arrays need to resist the force of wind hitting the panels from the rear.

Snow load is the relevant rating when it comes to hail. It’s usually listed in Pascals (Pa), a unit of force. Higher numbers are better.

A solar panel with an IEC 61215:2005 rating will have a snow load rating of at least 5,400 Pa and a wind load rating of at least 2,400 Pa. Panels that satisfy the older IEC 61215 standard only need a snow rating of 2,400 Pa.

Solar panel datasheets all formatted a little differently, so you’ll need to study it for a minute to find the rating. As an example, here’s a portion of the datasheet for the SunPower X-Series:

There are a couple things I’ve highlighted.

First is the IEC 61215 rating. (Unfortunately, SunPower hasn’t indicated whether it’s an older version of the standard or the newer 2005 standard.)

But below that, you can see the maximium load clearly listed. This particular product has two different frames.

SunPower’s Gen 3 meets the basic standard, but the Gen 5 frame is even stronger with an 8,000 Pa snow load rating. If you live in hail alley or somewhere with severe snowfall, the SunPower X-Series with a Gen 5 frame would be a good choice.

Consider stronger solar panels where hail is a risk

Even though standards like IEC 61215:2005 help ensure that solar panels will survive the majority of severe hail storms, if you live in hail alley or simply want to minimize your risk, it might be prudent to choose panels with an extra strong frontside rating.

The basic snow load rating you can expect in a modern solar panel is 5,400 Pa, but there are several on the market with even better ratings. Here’s a few:

These happen to be some of the most popular brands on the market, so the solar panel you want to buy might already be extra strength. If in doubt, be sure to ask your solar installer.

Are flat roofs at greater risk of hail damage? Maybe.

One thing to note is that hail damage testing is done with pellets fired straight at the panel. (You can also see this in the video above.) However, most roofs are sloped, which means that often hail will be hitting the panel at an angle.

An object hitting a flat surface at an angle doesn’t transfer all of its energy, which means most roof mounted solar panels could probably survive even larger than one-inch hail without damage.

However, if you have a flat roof, you might be at a higher risk because often the hail will be hitting your roof straight on. If that’s the case, you definitely might want to think about getting one of the stronger panels listed above.

This comes with a caveat, which is that hail is often accompanied by wind, which will drive the hail at a angle, making all of this a little unpredictable. Still, more often than not, flat roofs will likely be at a higher risk for solar damage than sloped roofs.

Summary: buying solar panels to survive hail

If you live somewhere with lots of snow, frequent hail, or even next door to a baseball diamond, you should factor in solar panel strength ratings to make sure that the product will stand up to hail, several feet of snow, or even flying baseballs.

Look for an IEC 61215 rating on the solar panel specification sheet and a snow load or frontside load rating of at least 5,400 Pa. If you choose a panel with a higher rating, you’ll have an even higher likelihood that your solar array will continue working decades from now.

Another thing to do is to call your insurance company to find out what coverages you have. Many insurance policies will cover hail damage to your home, and because solar panels are permanently fixed to the building, they should also be covered. But make sure to check with your insurance company first, ideally right after you have solar panels installed.

Further reading

• Facts about hail from NOAA
• IEC 61215: What it is and isn’t (from the NREL)
• 2009-01-22 Design qualification and type approval of PV modules acc. to IEC 61215:2005 / IEC 61646:2008