Solar farm hail damage is no longer a rare event that happens to someone else's site. In its 2025 Solar Risk Assessment, kWh Analytics reported that hail accounted for 73% of total solar loss dollars while making up just 6% of loss incidents. In other words, hail does not hit often, but when it does, it is the expensive one. For O&M technicians, that means storm response is a core part of the job at many utility-scale sites. This guide covers what you do before a storm, what to expect during it, and how to work a damaged site safely afterward.
Why Hail Matters So Much at Solar Farms
A utility-scale plant is acres of tempered glass held at an angle to the sky. The NREL/Sandia/SunSpec O&M best-practices guide lists hail among the environmental conditions O&M plans must account for, specifically for module breakage, alongside high wind, hurricanes and tornadoes.
kWh Analytics' findings sharpen the point for techs looking at where to work:
- Hail is the costliest peril by dollar amount, with fire second.
- 19% of hail-related losses in the 2025 report occurred in North Carolina, which is not a state most people think of as hail country.
- The company's 2026 edition looked at hail-hardened modules and tracker stow on a 100 MW single-axis tracker plant and concluded that both together are needed to keep losses acceptable across about 13% of the U.S.
The takeaway for your career: storm readiness and response skills are not just a Texas or Colorado thing. Any tech at a large tracker site should know the plan.
Before the Storm: Prep Work Techs Own
Most storm damage reduction happens on ordinary days. NREL's guidance on hurricanes and tornadoes (Section 5.7.3) lists pre-storm work that maps directly onto O&M routines:
- Fasteners. Inspect and re-torque fasteners across the system. NREL notes that many loose or missing fasteners have never been tested by real wind loads.
- Wire management. Replace weak or broken wire ties and add more where cables can whip or chafe.
- Debris. Remove anything that could become airborne: broken branches, abandoned stands, loose materials.
- Enclosures. Make sure cabinets and electrical boxes latch and their gaskets are intact; consider strapping doors on enclosures rated below NEMA 6.
- Instruments. Leave weather instruments recording if possible, but consider pulling anemometers and data antennas that you cannot replace quickly, since they often do not survive the worst storms.
Hail stow on trackers
On single-axis tracker sites, hail stow tilts modules to a steep angle so stones strike at a glancing angle instead of straight on. Techs keep stow working: tracker controllers communicating, motors and drives healthy, and weather triggers configured. A row that does not stow is unprotected. Our specializations guide covers why tracker skills are in demand.
Do not oversell stow. kWh Analytics found that physics-based models may overestimate stow's risk reduction by up to 48% for hail around 3 inches. Stow reduces damage; it does not prevent it. Plan your post-storm response as if some damage got through.
During the Storm: Stay Out of the Array
There is no repair task worth being in an open field during hail, lightning or high wind. Know your site's shelter location, keep vehicles out of the array, and monitor remotely if you can. Watch for communication loss, tracker position faults and inverter trips as early damage signals. Do not drive in until the storm has passed and your supervisor or the site plan says it is clear.
After the Storm, Step One: Make It Safe
NREL's post-event guidance puts safety first: trained, certified personnel in proper protective equipment should make the system safe by disconnecting damaged circuits, ideally at the module level, because ground and arc faults are likely. The guide also notes the O&M provider may be responsible for responding to storm damage and making the site safe.
Why broken modules mean fault risk: Mersen's technical note on PV protection lists impact damage and water ingress among the ways a cell can short to its grounded frame. A shattered module in sunlight is still generating voltage, and the next rain can turn cracked glass into a ground fault path. Our PV ground fault troubleshooting guide covers what to do when the inverter alarms afterward.
- Treat every damaged module and string as energized. Daylight means voltage.
- Expect inverter alarms and isolation faults; do not reset and restart blindly.
- Watch footing. Broken glass, washouts and debris make array aisles hazardous.
- Do not stack or handle broken modules without cut-resistant gloves and a plan for where they go.
Post-Storm Solar Inspection Checklist
Once circuits are safe, the work turns to finding and documenting damage. Use this as a working checklist, adapted to your site's procedures.
| Area | What to check | What to record |
|---|---|---|
| Modules | Shattered or crazed glass, cracked frames, dislodged modules | Block, row, string and module position; photos with a scale reference |
| Trackers and racking | Bent torque tubes, failed clamps, stuck rows, rows that did not reach stow | Tracker ID, position at time of storm if logged |
| DC wiring | Chafed or cut cables, loose connectors, damaged combiners | Location, insulation test results |
| Inverters and enclosures | Water ingress, damaged seals, alarm history | Fault codes with timestamps |
| Weather and comms | Anemometers, irradiance sensors, antennas | Which are offline or damaged |
| Site access | Washed-out roads, fence damage, downed debris | Photos and GPS points |
NREL lists the post-event sequence as: inspect the structure and electrical condition, document damage, prepare scopes and budgets for repair, then repair quickly to restore safe conditions and output. Good documentation from techs is what lets asset managers and insurers move fast. Your notes, photos and string maps become the claim.
Repair and Re-Commissioning
NREL recommends reinforcing or replacing failed components with stronger, properly engineered parts rather than identical weak ones, replacing bent parts, securing any modules that came loose, and making sure remaining rack sections are stable. Then it calls for re-commissioning the whole system before returning it to service.
In practice, that means the electrical testing you would do at startup: insulation resistance, polarity and open-circuit voltage checks, and string performance testing with an IV curve tracer where available. The NREL ground fault field guide also recommends infrared and visual inspection for overheated connectors and combiners. Techs with strong testing skills are the ones leading this work. See our diagnostic toolkit guide for the instruments.
What Storm Work Means for Your Career
Storm response often brings long days, overtime and travel, especially for regional or traveling crews sent to help a hard-hit site. It is also where supervisors see who can work methodically under pressure. Skills that stand out:
- Safe isolation of damaged strings without creating new faults
- Fast, accurate damage mapping that matches the site drawings
- Clean data for the claim: photos, IDs, test readings
- Tracker and stow system troubleshooting
- Testing for re-commissioning
If you are weighing a role at a big tracker site in hail-prone country, ask in the interview what the storm response plan is, who is on call, and how overtime is handled. Our local vs. traveling crew comparison has more questions worth asking.
Hidden Damage: What a Walkdown Misses
Shattered glass is easy to spot from a truck. Damage that is harder to see is what causes trouble weeks later. Mersen's protection note lists impact damage and water corrosion among the ways a cell can short to its grounded frame. That means a module with hairline cracks can look fine on a dry afternoon and still trip an inverter on the first damp morning.
The NREL ground fault field guide gives a few habits that apply directly to post-storm work:
- Use infrared and visual inspection together. NREL recommends both to find overheated connectors, combiner boxes and modules, since loose connections are a common source of arc faults.
- Compare insulation readings across circuits. A string reading a small fraction of its neighbors is suspect even if it passes a fixed threshold.
- Expect intermittent faults. The guide warns these are the hardest to find and may seem to clear while you test. Log them instead of writing them off.
- Keep baselines. Ground current and insulation readings from before the storm make it much easier to prove what changed.
Small leaks matter too. Fuse-based detection can miss low-level ground current, so a damaged string can keep running with a fault that no alarm reports. A careful post-storm test pass is the backstop.
Bottom Line
Solar farm hail damage is the most expensive problem a utility-scale plant faces, and O&M techs are the first people on the ground afterward. Do the boring prep (torque, wire ties, enclosures, working stow), stay out of the array during the storm, make the site safe before you inspect, document everything as if the claim depends on it, and re-commission before restart. Techs who handle storm response well become the ones employers trust with the rest of the site.