Whether it’s pigeons nesting underneath your solar array, cooing and scurrying around on your roof, or a family of squirrels who spend their days chewing on your system’s wiring—animals can threaten your solar generation as well as your peace of mind.

Thom Westergren, founder and CEO of Spiffy Solar noticed the prevalence of pigeons under solar electric rooftop arrays in east Denver and identified a need for hardware to keep birds and rodents out. “Pigeons don’t really harm the system, but they’ll get underneath and build a nest, which can retain water and damage the roof,” Westergren said. “It’s just a nuisance.”

Squirrels, on the other hand, are more destructive and can take down an entire solar system in minutes. Because they’re rodents, squirrels have teeth that grow throughout their lives, so they are regularly chewing and filing them down. “They happen to like the insulation on the wires, but they’ll also chew the connectors, which are harder plastic,” Westergren said. “I also have pictures of junction boxes on the back of panels that have been completely chewed off—including the insides.”

While squirrels and pigeons are most inclined to make a rooftop array their home, other pests can cause problems, including raccoons, possums and roof rats (especially in Arizona). Westergren has noticed the biggest problems in Colorado, New Jersey, Maryland and Toronto. “New Jersey has more solar than Colorado but the incidents are about double in Colorado,” he said. “It’s a matter of scarcity of habitat.” Critters are often an issue among solar homes on the edge of wooded land and open space, as well as new developments that offer untapped areas for animals to nest.  

It’s difficult to speculate where rodents will convene, and whether or not they’ll cause destruction. But if they do, and you own your solar system, the repairs aren’t covered by insurance and the bill often starts in the thousands. “If you’ve had a problem with squirrels, I’d say the average cost is $4,000 for the average size system,” Westergren said.

Martin LaMonica, writer for CNET, noticed squirrels scampering around his rooftop solar electric array. “I rationalized that perhaps they wouldn't cause any problems, even if they were nesting. When I had some work done on my chimney, I asked the contractor to clean out under the panels and hoped for the best,” LaMonica writes. He was forced to take action after determining the production levels for December were significantly lower than in previous years. “After some tests, my original installer quickly realized that one of the two strings of panels was disconnected. When he went onto the roof, he eventually discovered the root of the problem: chewed-off wires,” LaMonica recalled. “It took a while, but replacing those cables got the panels back to full power.”

Monitoring your system’s electric generation can help determine if productivity is being compromised. “Having somebody else, such as the installer, own the panels shifts that responsibility altogether, another reason why solar leases or power purchase agreements with solar installers are becoming more popular,” LaMonica points out.

Microinverters reveal how each individual solar panel is performing, but the entire system would still need to be inspected if a rodent issue is suspected. “A microinverter might actually make it worse because if you just have one panel go down—one or two—you might not notice it as soon,” Westergren speculated.

So what can the owner of a solar array do to limit bird and rodent problems?

The first line of defense is to trim trees and bushes, and remove any objects that would allow varmints to access the rooftop. The next step is to install a rodent guard, like the ones Spiffy Solar offers, made of PVC-coated, galvanized wire that is secured on the outside with hooks. One of the main goals when installing rodent protection is to refrain from drilling into the panels—which voids the panel manufacturer warranty—and avoid drilling into the roof, which can lead to leaks.

Aside from ensuring maximum efficiency, maintaining a rodent-free solar system can increase safety and peace of mind. Westergren recalled an incident where a homeowner in Maryland arrived just in time to see her roof smoking, thanks to the sparking wire gnawed apart by squirrels. 

As for solar leasing companies, Westergren says it’s a matter of weighing the risk to determine if preventative measures make financial sense. One company told him rodent damage occurred in half a percentage of installations in New Jersey and 1 percent of installations in Colorado. “That doesn’t sound like much, but you extend that over a 20-year lease and it turns into 20 percent,” Westergren said.