Yes. Pack rats chew wiring, and the gap between your solar panels and your roof deck is close to ideal habitat for them. If you live anywhere around Phoenix, Mesa, Chandler, or the foothill neighborhoods that back up to desert wash, this is not a rare freak occurrence. It is one of the more predictable ways a healthy solar array quietly starts underproducing.
The technical name is white-throated woodrat, but everyone here calls them pack rats. They are native, they are abundant, and they are relentless about collecting material and building sheltered middens.
Why the Space Under Your Panels Is Prime Real Estate
Think about what a pack rat wants. Shade during a 112 degree afternoon. Cover from hawks, owls, and coyotes. A dry spot that stays dry through monsoon downpours. A ceiling overhead and a flat floor underneath. Your array delivers all four at once, roughly four to six inches off the roof, with open sides for easy access.
Once one moves in, the midden grows fast. Pack rats haul in cholla joints, palm frond scraps, mesquite twigs, cardboard, insulation, and anything shiny they can drag. That pile sits directly against your roofing material and directly under the panels, where you cannot see it from the ground.
The Wiring Problem
Rodent incisors grow continuously, so gnawing is not optional for them. It is maintenance. Anything the right diameter to chew becomes a chew target, and solar DC home run wiring, module leads, and optimizer cables are exactly the right diameter. The insulation is soft polymer. It gives way easily.
What happens after a chew depends on what got exposed:
- Partial insulation loss. Nothing visible fails yet. The conductor is now exposed to weather and dust, and corrosion starts working on it.
- A severed conductor. A string drops offline. You see it in your monitoring app as a step down in production that never recovers.
- Ground fault. Exposed conductor touches racking or flashing. Your inverter faults out and shuts down the array, sometimes intermittently, which is maddening to diagnose.
- Arcing. The worst case. A damaged DC conductor can arc, and it is sitting inside a pile of bone dry desert kindling on a roof.
That last point is why this belongs in the same mental category as the bird nest fire risk homeowners already hear about. The fuel source and the ignition source are stacked on top of each other.
How to Tell You Have a Tenant
You can often spot the signs without ever getting on the roof. Look for these:
- Droppings, roughly rice grain size and dark, collecting on your walkway or patio below the roof edge
- Twigs, palm fiber, or cholla segments on the ground that clearly fell from above
- Greasy dark smudge trails on stucco, downspouts, or a block wall where the same route gets used nightly
- Scratching or scuffling sounds from the roof after dusk
- A string or a single panel showing a persistent production drop in your monitoring app
Pack rats are nocturnal, so you will rarely see the animal itself. You see the evidence.
Why Bird Proofing Mesh Also Solves the Rodent Problem
Here is the useful part. The same perimeter mesh that keeps pigeons from nesting under your array is, when installed correctly, an effective rodent exclusion barrier too. Both problems have the same solution because both animals exploit the same opening.
Installation details determine whether it actually works:
- Material matters. Galvanized or stainless mesh resists chewing. Plastic netting does not survive a determined pack rat.
- Full perimeter, no shortcuts. A single unclipped run along one edge becomes the front door. Rodents will find it faster than birds do.
- Tight to the roof plane. Rodents squeeze through gaps that look far too small. The mesh has to follow roof contours, not bridge over them.
- Attached to the module frame, not the roof. No new penetrations, which keeps your roof warranty and your roof intact.
One more thing that trips people up: exclusion only works on an empty array. If you seal mesh around an active midden, you have built a rodent a fortress. Clearing out the debris first is part of the job, and it is genuinely unpleasant work involving respiratory protection, because dried rodent droppings are not something to stir up casually.
Two Bits Solar Cleaning handles both halves. We clear nesting material and debris out from under the array, wash the panels with deionized water so no mineral film gets left behind, and install bird proofing mesh around the full perimeter so nothing moves back in. If you have heard scratching overhead or noticed your production numbers slipping, reach out and we will take a look at what is actually going on up there.