Squirrels Under Solar Panels: Something Is Living Up There

Why squirrels under solar panels pick that particular gap

Get a ladder to the edge of your array and look sideways underneath it. On a typical pitched-roof installation the modules sit on rails carried by flashed L-feet, and the underside of the glass ends up roughly three to six inches above the shingles. That clearance is deliberate: it lets air move behind the modules so they run cooler, and it gives the installer room to route conductors. It also creates a long, covered, continuous corridor running the entire footprint of the array.

Now picture that corridor the way an eastern gray squirrel does. It is shaded at midday and warm at dusk, because the modules soak up heat all afternoon and give it back slowly. It is dry, because the glass sheds rain and snow straight past the opening. It is out of the wind. Most importantly it has a roof, so a red-tailed hawk overhead or an owl hunting at first light cannot see what is moving underneath. That is a better den than most trees offer.

Birds nesting under solar panels, and the rest of the Pennsylvania cast

In Central and Eastern Pennsylvania the cast is short. The usual occupants are eastern gray squirrels and birds treating the gap as a ready-made nest cavity; chipmunks are ground-denning animals that only occasionally reach a low roof edge. Squirrels are the ones that chew conductors, which is why they change the electrical picture and the others mostly do not. The Pennsylvania Game Commission describes two gray squirrel breeding periods, late winter and midsummer — which is why a quiet array can turn noisy quickly, and why autumn brings animals looking for somewhere sheltered to spend the cold months.

Birds matter for a reason beyond the mess they leave. Three non-native species that commonly nest in roof cavities — house sparrows, European starlings and feral rock pigeons — are not protected under the federal Migratory Bird Treaty Act. Native birds use the gap too, and those are protected. State law applies as well: in Pennsylvania starlings and house sparrows have no closed season, but killing a banded homing pigeon is a separate offence, so check for a leg band before assuming a pigeon is feral. You cannot tell from droppings in a gutter which occupant you have, and the difference changes what may lawfully be removed and when. Identify the occupant before anyone touches a nest.

Solar panel wildlife damage, in order of seriousness

Start with the wiring, because that is the part that can do more than cost you production. Module leads and DC home-run conductors run through that gap, and rodents gnaw constantly to wear their incisors down. Chewing that severs a conductor or loosens a connection can start a series arc fault. Chewing that exposes a conductor without breaking it can instead produce a ground fault, or a parallel arc between conductors. NEC Article 690.11 requires a listed PV arc-fault circuit interrupter on DC circuits operating at 80 volts or more that are on or penetrating a building; which code edition applied depends on when your system was installed.

It is worth understanding what that protection actually does, and what it does not. A listed DC arc-fault interrupter watches for the electrical noise signature an arc produces, then shuts the circuit down and reports a fault. It detects and interrupts; it does not prevent. The required interrupters are series-arc detectors, so not every chewing-related fault will announce itself. And module-level systems with microinverters operate below the 80-volt threshold and are exempt entirely — on those arrays there is no DC arc-fault detector and no arc-fault code to warn you, so a quiet inverter is not evidence of undamaged wiring. Where a code does appear, it is not a nuisance to clear and forget: it is the system reporting that something in the DC wiring has changed, and under a rooftop array chewing is one credible reason why.

Below that hazard sits a longer list of problems that cost you output rather than threatening the house. None of them are visible from the driveway, which is the whole difficulty: everything that goes wrong under an array goes wrong in the one place on the property nobody inspects.

• Severed MC4 connectors on a string system, or a bitten microinverter trunk cable — either can take a single module, a string, or a whole branch circuit offline.
• Nesting material packed into the gap, trapping heat against modules that rely on airflow behind them to stay cool.
• Droppings and debris holding moisture against flashing, racking and fasteners, then washing into the gutters below.
• Nests and litter resting on the lower edge of cells, shading them and dragging output down disproportionately.
• Roof-surface damage under the array — lifted shingles, chewed underlayment — hidden exactly where nobody looks.

How squirrel-chewed solar wires show up in your monitoring and in your house

Wildlife damage rarely announces itself cleanly. What you usually see first is production that is lower than it should be without being obviously broken: a partial loss rather than a dead system, sometimes one module or one string dark in the monitoring portal while everything else reports normally. Damage that moves is the tell. If output dips on windy days and recovers when the air is still, a conductor with compromised insulation shifting against a rail or a frame is a reasonable suspicion to hold.

Inside the house the signs are older than any app. Scratching or scurrying overhead at first light and again at dusk, when squirrels are most active. Nesting material visible at the array edge or hanging below a module. Shells, droppings and shredded debris in the gutter under the lowest row. Any of these alongside a production drop is worth treating as one problem rather than two, and the same diagnostic ladder applies as with any <a href="/blog/solar-panels-not-producing-diagnosis">underperforming system</a>: read the monitoring first, then get eyes on the array. An arc-fault code is also worth separating from <a href="/blog/micro-inverter-failure-replacement">an inverter fault of its own</a> before assuming wildlife.

Why sealing the array shut before wildlife exclusion is the wrong first move

Here is the mistake that turns a manageable repair into a much worse job: running mesh around the perimeter while animals are still living inside it. Sealing the array closed traps them. They will chew to get out, usually through whatever is softest, which may well be the wiring you were trying to protect. If they do not get out, you now have a dead animal and a nest curing in the heat under your panels, and the only remedy is opening the array back up.

There is a legal dimension too. The Migratory Bird Treaty Act protects native migratory birds along with their active nests, eggs and young, while the three non-native species above fall outside it. Mammals are governed at state level, and in Pennsylvania gray squirrels are classified as game animals under Game Commission rules. Pennsylvania also requires a nuisance wildlife control operator permit to take or handle wildlife on someone else's behalf, so removal is work for the property owner or a permitted operator. This is general information, not legal advice — check the U.S. Fish and Wildlife Service on migratory birds and the Pennsylvania Game Commission on mammals, or ask a licensed wildlife control operator, before anything is removed.

Timing solves much of this. Work scheduled outside an active nesting period is kinder, legally simpler and faster, because the space is empty and nothing needs relocating. Early autumn is often a workable window in Pennsylvania, with summer litters dispersed and winter breeding not yet started, but the only way to know what is under your array right now is to look.

What a solar panel critter guard is, and how it is properly fitted

A critter guard is a physical barrier and nothing cleverer than that. It is mesh, commonly galvanized steel with a PVC coating because that is what survives weather on a roof, run around the exposed perimeter of the array, cut to follow the roofline and held with clips that grip the module frames. Half-inch aperture is the common choice for excluding squirrels and birds, and aperture should be selected for the animal you actually have, since what stops a pigeon will not necessarily stop a mouse or a juvenile squirrel.

Two constraints are worth stating plainly, because shortcuts here are common. Nothing gets drilled into a module frame: manufacturers generally treat drilling or modifying the frame as grounds to void the module warranty, and it breaks the anodized finish that keeps the aluminum from corroding. And done properly, a guard needs no new roof penetrations — every hole is a future leak. The mainstream kits clip to the module frames and come back off later without holes in the frame or the roof. If an installer proposes fastening into the roof deck, ask why before agreeing.

Be equally clear about what a guard does not do. It is not a repellent, a deterrent spray or a noise device. It closes an opening. If something is already living under your panels when the mesh goes on, the mesh keeps it there, which is exactly why the order of operations matters more than the product you choose.

The sequence of a proper critter guard job

A job done properly has a sequence, and the mesh is the last step rather than the first. The reason is simple: everything that needs repairing or removing sits on the far side of the barrier you are about to install. Get the order wrong and you either seal a fault in or have to cut the new guard back off within the month. The order the work should run in looks like this.

This is natural work to bundle with anything that already has the array off the roof or opened up. If a <a href="/blog/new-roof-with-solar-panels">panel detach and reset is happening for a reroof</a>, the under-array space is accessible and the wiring is already in a technician's hands, which makes it the easiest moment in the life of a system to deal with wildlife properly. The reverse deserves saying too: a guard fitted over unrepaired wiring fixes nothing at all. It just puts mesh between you and the fault.

• Inspect the full perimeter and the under-array space, identifying what is living there before anything is disturbed.
• Remove nesting material, stored food and droppings, and clear debris from the gap and the gutters below.
• Assess every conductor, module lead and connector for chewing, then repair or replace what is damaged.
• Exclude any remaining animals so nothing is trapped when the perimeter closes — in Pennsylvania that is work for the property owner or a permitted wildlife control operator, and we coordinate the timing around it.
• Fit the guard with frame clips, following the roofline so no gaps are left at the edges.
• Verify production and monitoring afterwards, confirming every module reports the way it should.

Critter guard maintenance, honest limits, and who covers wildlife damage

A guard is hardware on a roof and it lives a hardware's life. Wind-driven debris dents it, ice loads it, a falling branch can tear a section loose, and a determined animal will test the weak points: corners, valleys, anywhere the roof plane changes and the mesh has to follow a curve. Nobody can promise you an array that wildlife will never enter again. What a well-fitted guard does is close the easy routes and make the remaining ones visible while they are still small.

So look at it now and then. After significant storms, and at least once a year, check the perimeter from the ground with binoculars or have someone look while they are up there for something else. Pulled clips and bent mesh are easy to re-secure early and a real nuisance once something has moved back in behind them.

On the question everyone asks: whether wildlife damage is covered varies enough that a general answer is worthless. Some homeowner policies treat rodent damage as a maintenance exclusion and others do not, while module and inverter warranties generally address manufacturing defects rather than animal damage. Your own policy and warranty documents are the only place that question gets settled — ask your carrier or manufacturer directly rather than assuming either way.

Related: why your solar panels aren't producing · panel detach and reset for a new roof · micro-inverter failure and replacement · solar repair in Lancaster County · book a repair visit