Solar Info

Solar Animal Guard Job Cost Calculator

Whether you’re an installer in the field, or a manager at an installation company, you might want to get some insights into how much all your animal guard jobs cost, or when the AG Bender™ will pay for itself. Our job cost calculator can tell you all this and more.

Here’s what the calculator can do:

  • Get estimates on the amount of materials and labor required, and the costs associated with both.
  • See how much time and money the AG Bender will save you.
  • Get your nerd on by adjusting advanced settings like number of sub-arrays (this has a big impact on perimeter length & cost), labor rates and the multiplier for payroll taxes and other overhead.
  • All of these metrics are available on a per job and annual basis.

If you’re still unsure whether you should install animal guard at all, or if you need some help convincing a customer to take the step, you should check out the first part of this series called “Does my solar PV system need animal/critter guard?“. Here we explore the financial risks of not installing animal guard.

Also, refer to our sourcing guide for all the best materials and tools to use when installing animal guard. We don’t sell the tools listed here, we simply hope you get some value out of the guide.

The Slick Tools Team

Solar Info

Does my solar PV system need animal/critter guard?

Whether you’re a solar homeowner, installer or investor, you’re likely aware that pests – namely squirrels and birds – can mess with solar systems. Search the internet, and you’ll find a wide range of conflicting anecdotes and industry practices:

  • Horror stories from homeowners who’ve dealt with roof leaks and expensive repairs due to squirrels
  • Homeowners who’ve had no animal issues after decades of PV system ownership
  • Solar installers who include a protective animal barrier on every PV system they sell
  • Solar installers who sell PV systems without mentioning animal guard (or charge an additional fee to install it)

With no clear consensus on the utility of animal guard, the decision of whether to invest in it can be a tough call. Rather than throw more anecdotes at you, we’ve decided to approach this question the same way we would any business investment – using math and any hard data we can get our hands on!

The Equation

We’ll start with a simple premise: animal guard is worth installing if the money it saves (by avoiding nest removals, repairs, and lost production) exceeds the cost of installation.

Cost of animal damage > Animal guard install cost

In this article, we focus exclusively on the left side of the equation – the cost you can expect to incur if you don’t install animal guard. To estimate the cost of installing animal guard, gather quotes from local contractors or estimate the cost of doing it yourself using the resources on our website.


Short on time? Here are ballpark numbers to guide your animal guard decision:

  • We estimate the typical US residential PV system owner will be liable for $855 (net present value) in animal-related costs over the lifetime of the PV system should they choose not to install animal guard. These costs include nest removal, inspection, repair of animal damage, and PV production losses due to animal damage.
  • Our simulations show a standard deviation of $1,200 in liability, with the best case resulting in zero costs and the worst case over $9,000.
  • We expect about 60% of PV systems to experience at least one animal-damage event over a 30-year lifetime, with any such event requiring professional inspection and remediation.

If you’re curious how we came up with those numbers, or would like to tweak our assumptions and run your own simulation– in other words, if you’re a nerd like us– read on!

Animal Damage Scenarios

As we heard earlier, the cost of animal damage can vary widely. Factors affecting it include:

  • Geographic location and amount of squirrel/bird activity
  • Accessibility of PV system to animals (e.g. overhanging trees, roof height)
  • Local contractor rates for inspection and repairs

That said, we can make a reasonable estimate by breaking down the various animal-damage scenarios and estimating their costs and likelihoods. Consider a single year in the life of a PV system. Here are four different ways the year could play out animal-wise:

  1. No animal activity/damage. There are no costs incurred because no animal decides to venture under the PV array.
  2. An animal nests under the array and is detected quickly. A service technician is brought to the site to remove the nest. Because nests frequently result in damage to the roof or PV system, the technician must inspect the nest area for damage, which involves temporarily shutting off the PV system and removing several solar panels for access. Because nests restrict airflow under the solar array and increase PV cell temperature, the system power output will have suffered during the presence of the nest – but only for a short time.
  3. An animal nests, resulting in minor damage to the PV system or roof. See our breakdown of common animal damage. Repairs often include replacing wires whose insulation has been chewed through by rodents, replacing an individual panel whose backsheet has been scratched, and re-roofing portions of the roof where a nesting animal has scratched through the surface.
  4. An animal nest goes undetected until secondary damage has occurred. Secondary damage includes water damage and mold due to a compromised roof surface, long-term performance degradation of the PV system, and fire and electrocution hazards due to compromised electrical insulation and PV hot spots. All of these would require extensive repairs.

Likelihood of Damage

Having established these four possible outcomes, how likely is each to occur for a PV system without animal guard? We’ve been unable to track down reliable statistics around this, so let’s make some conservative guesses:

EventChance of occurrence
(over 1 year)
Nesting; no damage2%
Nesting; minor damage1%
Nesting; secondary damage0.1%
No damage96.9%

I.e. we’re estimating that in any given year, there is a 1-in-50 chance (2%) that an animal nests under the array but is removed with no further consequences. These figures will certainly vary by location, but we feel the numbers above represent a normal area with moderate critter activity. If you’re interested in a location where you know the risk to be higher (or lower), you’ll have an opportunity to plug in your own numbers later.

Cost of inspection & repair

Next, let’s estimate the cost of dealing with each of the outcomes listed above. Consider the potential elements of any response:

A local service manager tells us: “If there are live animals nesting under an array (or an extensive animal mess that needs proper PPE to clean up) it can result in needing to hire animal control since service technicians are not armed with the knowledge or PPE to deal with this sort of issue.”
  • Van roll – In contractor-speak, this means having to send a qualified person (e.g. a licensed electrician) and helpers to the job site– which costs money regardless of any work performed. Typical cost: $200
  • Panel removal/inspection – If any animal activity (or debris buildup) is detected under the array, nearby solar panels must be lifted to inspect for roof rot and damage to the PV wiring. Typical cost: $200
  • Minor roof/PV repairs – Removing nests, replacing chewed wires and compromised roofing, re-commissioning system. Typical cost: $800
  • Major repairs – Interior mold remediation, PV module or electronics replacement. Typical cost: $5,000
  • Lost production – Reduced PV output and downtime due to hot spots over nests and chewed wire insulation. In a 2020 report based on observing 100,000 PV systems, NREL found that “damage caused by animals may not occur often, but… can have substantial impact on annual production.” This is because damage that reduces PV performance, but does not actually shut the system down, may go undetected for years. We’ll assume lost production equals 25% of expected production during the year in which animal damage occurs. For the average residential rooftop system, that is about (9,000 kWh)*(25%)*($.14/kWh)= Typical cost: $315
How did we arrive at these cost figures?

We surveyed our network of solar installers to determine typical service costs. These costs can be extremely variable based on location, supply and demand. For example, here in Colorado we occasionally have a bad hail storm that causes a jump in service rates and lead times. Here are the ranges we’ve found contractors are charging across the US:

  • Van roll – $150-$500
  • Hourly service rate – $180 (waiting for more data)

Note these amounts reflect the direct costs (labor and materials) a contractor would incur to perform the work. The amount billed to the customer (homeowner, lessor or warrantor) would also include the contractor’s profit margin and taxes.

There is one additional, difficult-to-quantify cost of any maintenance incident with a PV array: reputational damage to the installer, lessor or system owner (if other than the homeowner). Homeowners who encounter unexpected problems with their PV systems tend to share their experiences, and are less likely to refer friends and neighbors to the companies they dealt with. For this reason, some solar installers now include animal guard with every new PV install, rather than quoting it separately and giving the customer a choice.

Other Model Parameters

Let’s round out our hypothetical situation with these parameters:

  • Remaining PV years of service – For this demonstration, we’ll assume we are a homeowner considering adding AG on a new PV installation which we expect to produce electricity for 30 years. If your PV system is a decade old and you’re considering an AG retrofit, you might reduce this to 10 or 20 years.
  • Discount rate – We’ll discount future costs using this rate to reflect the time value of money. Our results will all be stated in terms of Net Present Value (today’s dollars). Note the discount rate represents opportunity cost, but not inflation – since solar service costs are likely to rise with inflation.
  • Contractor profit – In our example situation, we are a homeowner who expects to pay a 20% premium above the contractor’s direct labor & materials costs. If we were instead a contractor estimating the cost of offering our customers an animal-damage guarantee, we would zero this value.

Putting it all together, we have the following model:

Want to tweak these numbers to reflect your situation? Click here to open a read-only version of our Google Spreadsheet – then save your own copy and edit the yellow fields as you like.


Our spreadsheet performs 1,000 simulations of the 30-year lifetime of our model PV system, calculating the costs incurred for each year and summing them in terms of today’s dollars. The histogram below shows the odds of a single PV system’s lifetime animal-related costs falling into various bins.

The first leftmost blue column tells us there is a ~50% chance that our model PV system will incur <$500 in animal-related costs over its lifetime. The second column tells us there’s a ~20% chance those costs will fall in the $500-$1000 range – and so on. If you were to add all columns together, they would equal 100%.

As you can see, there is a decent chance that lifetime costs will be less than $500, but a significant “tail” of higher-cost outcomes. Analyzing the results further:

The key figure here is the mean, or expected value, of lifetime animal-related costs – $855. According to our initial equation, we should install animal guard if it can be done for $855 or less. However, consider two scenarios:

  1. We do NOT install animal guard. We will probably incur $855 NPV costs over the lifetime of our system. However, the actual cost could be slightly lower (as low as $0) or significantly higher (our simulation’s worst case was ~$9,300).
  2. We DO install animal guard at a cost of $855. Assuming a quality installation, we have little risk of animal issues for the lifetime of the system.

Choice #2 involves the same expected cost as choice #1, but with less variation (or risk), making it a better investment all else being equal. For most investors, it would make sense to pay some premium over $855 for animal guard in order to eliminate this uncertainty.

Another interesting result is that while the odds of having zero animal issues in any given year are 96.9%, the odds of getting away scot-free for all 30 years are only 39%. In other words, the majority – 61% – of PV systems are expected to have at least one animal-related event during their lifetime.

Other Factors to Consider

Armed with the information in this article, readers should consider a few more factors before deciding whether to install animal guard:

For the homeowner:
Raccoons have been known to scratch holes clean through roofs.
  • Some homeowners will look at the numbers in this article and think it is a no-brainer to leave their system unprotected; after all, there is a decent chance they’ll have zero animal problems, so why not avoid the up-front cost of installation?
  • Others will see animal guard as an obvious winner, since it eliminates potentially huge costs and stabilizes the return on investment of their PV system.
  • Homeowners looking to buy a new PV system may stand to gain the most from animal guard installation, because it will protect the system for longer and cost less to install (since the installer will already be on the roof). Those seeking to retrofit AG onto an existing PV system will not have these advantages, but may still find the job worthwhile.
  • Of course, there is also the option of doing it yourself – the materials for which will cost a fraction of the expected animal-damage cost. However, great care must be taken to ensure a reliable result.
  • Will homeowner’s insurance help cover animal damage under your PV system? We asked a solar service manager here in Colorado. She told us, “We have seen instances (very few though) that an animal got through AG through sheer force (raccoons in particular). If a homeowner can prove that the damage was incurred by specifically a raccoon, repairs may be covered under homeowner insurance, but they do not cover bird, squirrel, or rat damages.”
For the installer:
  • Most warranties offered from installer to homeowner do not include animal damage, so the installer is not on the hook for repairs. However, homeowners are expecting a good experience from their solar install and will associate any unexpected problems – animal or otherwise – with the installer. If your customers will not stomach an extra fee to install animal guard, is it worth doing it anyway to reduce call-backs and increase customer referrals?
  • How much does it actually cost to install animal guard? With the right tools, materials and training, the cost might be lower than you expect. Use our job cost calculator to estimate the cost of your animal guard install.
  • Do your competitors offer animal guard? Installing it by default or as an affordable add-on could set you apart.
For the investor or lessor:
  • If you own many PV systems, then you’re likely not concerned with the large variance in each system’s lifetime animal-damage costs; your portfolio-wide average cost will probably be close to the mean.
  • However, with your return on investment riding on the accuracy of that mean, some due diligence is required. Does the geographical area that you’re investing in have higher or lower animal activity than the “typical” situation described in this article? Are contractor rates higher or lower?
  • Are you or the homeowner responsible for maintaining the system and monitoring performance? How likely is a homeowner to notice or notify you of animal activity on their roof? Should the homeowner have a bad experience with an animal infestation, could it hurt your reputation?
  • If you’re contracting out a large number of PV installations, you can likely have animal guard installed at a very low per-system cost.

We hope this article answered some of your questions and gives you a firmer footing to make your animal guard decision! Check out our other animal guard information for tips that will help you get the most out of your (or your customer’s) PV system.


The Slick Tools Team

Solar Info

Built to last

This Animal Guard Bender has been with Namasté Solar for 2 years now, and it’s still going strong! In fact, we have not had any warranty claims on these tools. Davis at Namasté Solar had this to say about the AG Bender:

“It’s held up to the abuse it gets in the work van and looks like it will be around for a long time.”

Davis Fogerty – Solar PV Installer, Namasté Solar Electric

Slick Tools was founded to help solar installers, and to make their jobs easier. The last thing we want, is for our customers to worry about the reliability of their tools. Therefore, we chose durable materials that can last for years and designed the Bender in such a way that parts can easily be replaced. This dedication to quality, coupled with our hand assembly of each Bender makes for a tool that will last.

Hand assembly of an Animal Guard Bender

Installers using the AG Bender in the field noticed that pulling the mesh through the machine, slowly wore off the contact rods over time. Back then, Benders were outfitted with contact rods made out of durable polyethylene (UHMW) and we found that by simply rotating the rods, installers could get the maximum use out of the parts.

Since then, we have found that the materials Teflon™ and Delrin™ are better suited for most mesh types. While we have not observed any substantial wear on the current rods, we do offer replacement parts in our shop. These can easily be swapped out by the customer.

Additionally, we have a warranty for the unlikely event of a Bender being defect or not performing like it should be.

As always, reach out with any questions or comments you have!

Happy Bending,

The Slick Tools Team

Solar Info

Mind the Gap – How NOT to Install Solar Animal Guard

This is the second post in our series explaining common mistakes and animal guard failure modes.

When it comes to installing solar animal guard, the old saying applies: Do it right or do it twice. There is nothing worse than spending the time and money to install critter guard, only to have an animal sneak in and build a nest anyway. This can happen if the installer leaves too large of a gap between the fencing and the roof/array, creating an incomplete seal.

Maximum Gap Size

To prevent this from happening, solar contractors should maintain a clear, company-wide standard of 1/2″ maximum gap between wire mesh and other objects (such as the roof, PV modules and protruding rails or conduit). 1/2″ matches the wire spacing of industry standard wire mesh, which has proven effective at blocking small critters.

Allow no more than a 1/2″ gap to ensure animals can’t sneak through.

You may be wondering if animals can get under the PV array through the gaps between the solar panels themselves. These gaps are determined by the racking system used to attach the panels to the roof, and can be as large as 1″ (for UniRac SolarMount). Though many rodents can squeeze through a 1″ gap, we have yet to hear a report of this happening. Please share in the Comments if you have observed otherwise!

Now let’s take a look at some violations of the 1/2″ rule and see how they could be avoided.

Rail & Conduit Penetrations

90% of rooftop solar systems have some sort of object(s) sticking out from the array around the edges, such as rail ends, conduit, roof vents and junction boxes. These interrupt the uniform gap between roof and array, and must be worked around when installing animal guard.

In the photo above, the wire mesh is cut and attached to each side of a rail. Obviously, this leaves a huge gap under the rail. The mesh is also poorly supported and could be peeled back by a rodent. Below is another shoddy approach to rail ends that failed and led to pest incursion.


Cut small “windows” around penetrations and leave the mesh as intact as possible, as shown below in a still from the Rail Mount Method instruction video.

Sometimes you need to cut a slit in the mesh to fit around a piece of conduit. After installing the mesh, Be sure to “stitch” the slit back together with hog rings or metal (never plastic) zip ties.

Flat & Floppy Wire Mesh

When wire mesh is installed as a flat piece of material with no bends in it, it is floppy and unstable. This presents three problems:

  1. The mesh tends to be “wavy” after being installed, creating unacceptable gaps.
  2. The waviness looks unprofessional.
  3. When flat, the mesh has no rigidity and can be peeled back or pushed in easily by snow and critters.

This video clip illustrates the third point:


Crease the wire mesh into an L- or C-channel before fastening it in place. This gives it 3-dimensional stability and eliminates waviness.

A wire mesh C-channel has a professional appearance and no waves or gaps.

Railless racking systems

“Railless” racking systems are intended to speed PV system installation and use less materials to reduce costs. Unfortunately, they make it particularly difficult to keep pests out from under the solar array.

Roof Tech’s E Mount AIR and Apex products require short, hollow aluminum channels to be installed around the array perimeter. Unfortunately these act as “rat tunnels” and are difficult to seal as shown below.

Zep (now owned by Tesla) and IronRidge FX are two other railless racking systems that pose a similar problem due to their irregularly-shaped roof attachments protruding from under the array.


The best solution we’ve heard of for sealing these systems is to build an external “cage” around any hardware protruding from under the array.

While this method works, it is not as secure or discreet as a C-channel tucked under the array. The wire mesh is out in the open and may be vulnerable to damage by wind-blown branches and snow loads.

Tile Roofs

Tile roofs require extra time and attention to adequately seal with wire mesh. The gap shown here is unacceptable, as small rodents and birds can easily squeeze through.

Tile roofs are the bane of every animal guard installer’s existence! Whether they are flat concrete tiles, S-tiles or trapezoidal, tiles create an uneven surface that is difficult to seal. Unfortunately, the only way to seal an array over a tile roof is to cut slits in the wire mesh and bend it to match each step in the tiles. It’s a slow but necessary task; small birds and rodents can and will enter through gaps around tiles.


There is one trick that will speed up the process of conforming wire mesh to a tile roof and ensure the best possible seal. Rather than attempting to cut the wire mesh perfectly to match the roof, bend a 1-2 inch “flange” into the wire mesh where it meets the roof. Then cut slits into the flange, and bend the flange down to meet the roof. Bending the flange gives you more room for error in your cuts, as the flange can take up as much or as little space as needed. The flange also lends some rigidity to an edge that would otherwise be floppy and unstable where it meets the roof.

Metal Roofs

How not to install animal guard over a standing seam metal roof. (1) leave “bays” between standing seams open to pest intrusion, (2) leave large gaps or flimsy patches around rail protrusions, (3) use plastic zip ties.

PV systems over metal roofs are the most difficult type to seal. As shown in the photo above, standing seams create an uneven surface just like a tile roof– but unlike tile roofs, we cannot allow the wire mesh to touch and scratch the painted roof surface. We don’t know any installers who are 100% confident of their method for metal roofs, and many are refusing to install animal guard over metal. Several companies (including Slick Tools) are working to develop products that address this need; sign up for our email list to be the first to hear about them!

That said, protecting metal-roof PV systems from animal damage is possible. We’re going to devote our next article to this topic, including a breakdown of our recommended method, little-known facts about metal roof warranties, and an installer horror story!

Thanks for reading, and good luck out there!

Solar Info

Cutting Corners – How NOT to Install Solar Animal Guard

This is the first in a series explaining common mistakes and animal guard failure modes.

In the photo below, wire mesh wraps around the outside corner of a solar array. At the corner, the mesh has been partially cut through, leaving a large gap for animals to pass through. Unfortunately, this is a common mistake. How did it happen?

The wire mesh was cut at this corner and left without a patch – providing easy access to pests.

The answer has to do with the J-hooks that attach the wire mesh to the solar panels. For J-hooks to hold wire mesh in place, the mesh MUST splay out from the array and be supported by the roof, as illustrated below.

This outward splay is necessary because unlike SnapNrack or CritterBlok, J-hooks do not fully support the mesh. If the wire mesh were suspended above the roof, there would be nothing to stop it from getting pushed under the array by animals, snow or wind.

Because of this splay, a slit must be cut into the mesh when wrapping it around a corner.

Most J-hook manufacturers recommend patching each corner using an extra piece of wire mesh and zip ties. Unfortunately, these patches are ugly, unreliable and time consuming to install. Unscrupulous installers will not bother with the patch, as we saw above. Even if a patch is applied, it will only last as long as the fasteners holding it in place (about 2-5 years for plastic zip ties in our experience).

This outside corner was patched with a piece of wire mesh, but the patch was secured with plastic zip ties. The zip ties broke after a couple years in the sun, allowing an animal to enter and build a nest.

Here are several ways to avoid all of these problems:

Solution 1: Don’t use J-hooks

Whenever possible, we recommend the Rail Mount Method or a full-support clip like CritterBlok instead of J-hooks. Those methods allow wire mesh to wrap cleanly and continuously around corners with no splay.

Wire mesh C-channels make for crisp, continuous corners – no patching or zip ties required.

Solution 2: Use wire mesh C-channels with J-hooks

Sometimes you are stuck with J-hooks – for example, when installing animal guard to a railless PV system. In these situations, use wire mesh C-channels instead of the traditional L channel. In addition to getting clean, patch-free corners, your entire pest barrier will be more durable.

Just like the Rail Mount Method, the wire mesh is bent into C-channels on the ground and tucked into place between the roof and the PV array. However, attachment is done with J-hooks instead of self-tapping screws. At each J-hook location, cut a small tab in the upper flange of the C-channel, so that the tab presses against the outside edge of the PV module. This keeps the wire mesh from being pushed under the array. Below are some examples of the finished product.

Solution 3: Secure patches with metal hardware

If you absolutely need to patch a corner, do not use plastic zip ties. Instead, use hog rings which are faster to install and will last for decades. Check out our AG Sourcing Guide for more info on hog rings and stainless zip ties, which are another good option.

We hope this info saves you and your team time and money! Share with your coworkers using the links below, and join our email list to get notified as we continue this series.

Solar Info

New Instruction Video: Installing Solar Animal Guard with the Rail Mount Method

When I started designing and manufacturing tools for the solar industry, it quickly became clear that making great tools would only be a small part of the job. The real work would be to educate installers and operations managers around best practices to drive demand for these tools. It’s a roundabout form of marketing that requires a big up-front investment from Slick Tools, but I hope that educational materials like the video below will boost installer pride, profitability and willingness to invest in best-in-class equipment. And hey– if no one buys our tools, at least we’ll have made a few installers’ lives easier and accelerated the growth of clean energy!

On that note, I am thrilled to share the fruit of what has been a months-long effort to build a high quality, technically detailed instruction video on installing solar PV animal guard. The video demonstrates what I call the Rail Mount Method, which I learned at Namaste Solar Electric during my time as an installer there. I was surprised to find that very few other installers around the country are using technique. After studying every animal guard product and installation method on the market and speaking with a number of industry veterans, I feel this is simply the best method to install long-lasting animal guard for most situations.

A wide range of neighbors, friends, family and former coworkers helped make this video possible – from lending a leaf blower to clear unexpected snow off the array on shoot day, to providing dozens of hours of editing time at a “buddy” rate. In particular, thanks to Mark who allowed us to film on his roof; David and Tage from My Storyline, who filmed the video; and Joe Sherman who edited the footage!

Watch the video below and learn more about the Rail Mount Method at its dedicated web page.

Solar Info

Announcing the Solar Animal Guard Sourcing Guide

Today we’re excited to share a section of our website that has been in the works for months! The Solar Animal Guard Sourcing Guide contains a breakdown of the most popular animal guard materials and tools on the market. Its main target audience is procurement folks at solar installation companies, but we expect this info to be super helpful for DIY-minded solar homeowners as well.

The Guide contains a section on each major component – the wire mesh, the fasteners, etc. For each section, we explain what to look for in that component – such as material, attachment style and other features. Then we provide our recommended product based on input from our installer network across the US. Finally, we list all the other options and their pricing. We’ve identified the lowest-cost retailer/distributor we could find for each product (Slick Tools does not distribute any of these products ourselves, other than the AG Bender).

We will continue to update this guide as new products come on the market and prices change. If you’re a manufacturer or distributor who would like to recommend an update or addition to the Guide, reach out and we would be happy to include you. There are no fees or strings attached, and we’ll make our best effort to objectively highlight the benefits and drawbacks of every product.

Finding the right tools and materials is just one piece of the animal guard puzzle. Stay tuned as we continue to publish resources like this for the solar community, including an upcoming step-by-step instructional video on AG installation!

Solar Info

How Pests Damage Solar PV Systems

Thanks to prolific service technician Michael Payton for many of these fantastic images!


Animals build nests under solar arrays because the arrays provide shelter from predators and the elements. Nesting is a precursor to every form of damage described below. Squirrels, birds, rats and raccoons are the main offenders.

Primary Damage

Chewed wires

Squirrels, rats and other rodents must regularly gnaw on material of a particular hardness in order to sharpen their teeth. The vast majority of modern PV systems have exposed wires underneath the array which cannot be enclosed in conduit. These wires have a thick coat of insulation which is, unfortunately, irresistible to rodents. Note – you may have heard of the phenomenon of rodents being drawn to soy-based wire insulation. Whether or not those stories are true, soy is not an ingredient in the tightly regulated wiring used in modern PV systems.

Once an energized wire’s insulation has been chewed through, there is a risk of fire, electrocution and lost production.

Roof rot

Most roof surfaces are will slowly degrade if moisture is continually present. When an animal builds a nest under the solar array – or sticks and leaves simply blow in and accumulate – the organic material retains moisture and prevents normal drying. Nesting animals also have a tendency to scratch away the roofing material at the nest site (both squirrels and raccoons have been known to burrow clear through the roof and into the attic). This leads to water damage.

Hot spots

Every solar PV array performs best when it’s kept at a low, uniform temperature. When a nest reduces airflow at one location under the array, a few individual PV cells heat up and become restrictive to the flow of electrons through the system. This causes them to heat up even more, creating a “hot spot” with an outsize impact on system performance. The presence of a hot spot may also increase fire risk, with under-array temperatures routinely reaching 150°F even for normally-functioning systems.

Secondary Damage

Water damage

When the waterproofing membrane of a roof is compromised due to roof rot or animal burrowing, water can enter the home and cause direct damage to drywall and paint as well as long-term mold issues.


While PV-related fires are extremely rare, they have occurred. Nearly all documented cases we’ve found were the result of wires or connectors being damaged or improperly installed, such that current flowing through them was restricted but not cut off completely. Such a restriction converts electrical energy to heat, and can ignite nearby materials. Unfortunately, a restriction in normally-current-carrying conductors (as opposed to an outright severance or ground fault) will not trigger any safety mechanism – allowing the problem to continue unnoticed. Roofing materials and PV components are designed to be fire-resistant, but the organic materials of a nest can ignite easily.

Electrocution hazards

When the insulation around an energized conductor is compromised, that conductor presents an electrocution risk to anyone who comes in contact with it. This risk is amplified when the conductor comes into electrical contact (e.g. when it rains or snows) with other metal components of the PV system, such as the racking or module frames. Modern, code-compliant PV systems include a safety mechanism that will shut down the system if such a ground fault is detected, making this more of a lost production hazard than a safety hazard. However, ground-fault protection systems do not always function as intended, and older inverters may lack protection and require replacement if there is a ground fault. Any PV system with suspected insulation damage should be deenergized immediately.

Lost production

In a 2020 report based on observations of 100,000 PV systems over 5+ years, the National Renewable Energy Laboratory found that “damage caused by animals may not occur often, but… can have substantial impact on annual production.” The report tracked lost production specifically attributable to pests, and found an average 28% production loss during the year in which the animal-related event occurred. For reference, this would represent a loss of about $350 for the average US residential PV system.

When a PV system stops operating entirely due to a ground fault, broken conductor, or during repairs, it of course stops generating income and reduces the system’s return on investment. Such disruptions often take longer than expected to fix due to high demand and low supply of solar service technicians.

A bigger problem, though, is when system output is reduced due to animal activity but not stopped entirely. This is likely to go undetected by the system owner because solar PV production is so variable to begin with (due to weather, temperature and other effects). Production losses can then persist for years.

What to do about it

Phew… now for some good news!

All of the hazards described above can be virtually eliminated through the careful installation of a good quality solar animal guard. This is best done by an experienced professional, but homeowners on a budget can do it themselves.

Explore the resources on our site for homeowners, installers and investors to decide whether animal guard is worth the investment, and how to perform a top-quality install.