Solar panels are engineered to convert sunlight into electricity with minimal maintenance, but like any electrical system, they occasionally encounter problems that reduce output or stop production entirely. When your solar panels aren’t generating expected power, diagnosing the issue quickly can minimize lost energy and protect your investment. This guide walks you through the most common solar panel problems, how to identify them, and when to call a professional.

The majority of solar panel issues fall into a handful of categories: inverter faults, shading and soiling, wiring and connection problems, weather damage, and age-related degradation. Learning to recognize these symptoms will save you money on service calls and help you communicate clearly with your installer when professional help is needed.

Check Your Inverter First

The inverter is the most common point of failure in a residential solar system. Located between your panels and the electrical panel, it converts direct current (DC) power from the panels into alternating current (AC) power for your home. Most inverters display status lights or error codes when problems occur. Check the display for red, orange, or blinking indicators—your manual should explain what each code means. Common inverter codes include ground faults (insulation failures), overvoltage, overtemperature, and communication errors with the grid.

If your inverter is displaying a fault code, take a photo of it and contact your installer. Do not attempt to reset the unit multiple times, as this can worsen some faults. Modern string inverters (the most common residential type) typically last 10-15 years before needing replacement, so if your system is over a decade old, inverter failure should be high on the diagnostic list. Microinverters (inverters installed on each panel) tend to be more reliable individually but failure of even one unit will eliminate that panel’s output.

Inspect for Physical Shading

Even partial shading from trees, buildings, chimneys, or newly installed structures can dramatically reduce panel output. A shadow covering just 25% of one panel in a string can reduce the entire string’s output by up to 75%, depending on your system’s electrical configuration. Walk around your roof and panels during the times of day when shading is most likely—early morning and late afternoon in summer.

Look for new trees that have grown into the line of sight since installation, branches overhanging the roof, or neighboring construction. If shading is the culprit, contact your installer about repositioning panels (if mounting allows) or trimming vegetation. For permanent shading situations, some homeowners invest in microinverters or power optimizers, which mitigate (but don’t eliminate) the impact of partial shading.

Clean the Panels and Check for Soiling

A layer of dust, pollen, bird droppings, or dirt on your panels reduces light penetration and output. In arid regions with infrequent rain, soiling can reduce efficiency by 3-7%. In areas with regular rainfall, soiling is less of an issue, but farms, industrial zones, and desert climates experience more buildup. You can clean panels yourself with a soft-bristle brush and deionized water, or hire a professional cleaning service for $150-$300 per system.

Before climbing on your roof, ensure your safety—use proper fall protection or hire trained cleaners. Avoid abrasive materials and high-pressure washers, which can damage the anti-reflective coating or seals. Early morning or late afternoon cleaning works best, as water evaporates slowly and allows more complete surface coverage. Clean quarterly or after dust storms for maximum benefit.

Examine Wiring and Connectors

Solar systems contain dozens of connection points—at the panels themselves, in junction boxes, at combiner boxes, and throughout the DC and AC wiring. Loose or corroded connectors cause voltage drop and power loss. Visible signs include burn marks, discoloration, or loose-looking wires at connection points. These are serious fire hazards and should be addressed by a qualified electrician immediately.

Weather, thermal cycling (expansion and contraction from temperature swings), and age can loosen connections over time. Your annual maintenance should include a visual inspection of all accessible junction boxes and connectors. If you see corrosion (a white or green crusty buildup), water intrusion, or signs of arcing (black discoloration), contact your installer to have the affected components replaced or re-seated.

Test DC Voltage with a Multimeter

If your inverter is displaying no fault but production is still low, you can measure DC voltage at the panel level to verify power generation. Using a multimeter set to DC voltage mode, test the positive and negative leads at a visible junction box or combiner box during sunny conditions. A healthy panel string operating in full sunlight should produce between 300-600 volts DC, depending on the number of panels in series. If you’re getting significantly lower readings, shading, soiling, or cell failure may be responsible.

This test requires basic electrical safety awareness—never touch bare wires or terminals, and always use insulated tools. If you’re uncomfortable with a multimeter, ask your installer to perform this check. The results will help pinpoint whether the problem is on the DC (panel) side or AC (grid connection) side of your system.

Look for Microcracks and Cell Damage

Solar cells are made of silicon, which is brittle. Impact from hail, falling branches, or manufacturing defects can create microcracks—hairline fractures inside the cell that reduce its ability to generate current. Microcracks often aren’t visible from ground level but show up as dark lines or discoloration under infrared imaging. If you suspect hail damage or impact, contact your installer to request a thermal image survey.

Most residential solar panels come with a 25-30 year performance warranty that covers defects in workmanship or materials, including cell cracks. If your panels are relatively new and show signs of damage, file a warranty claim with your installer or the manufacturer. Major damage is rare on modern panels, which are rated to withstand hail up to 1.25 inches (IEC 61215 standard), but it does happen.

Monitor Temperature and Thermal Cycling

Solar panels work more efficiently in cool conditions—each 1 degree Celsius above 25C (77F) reduces output by approximately 0.4-0.5%. In summer, roof-mounted panels can exceed 65C (150F), cutting output by 15-20% compared to STC (Standard Test Conditions). This is normal and not a malfunction, but understanding this temperature effect helps you set realistic production expectations for hot months.

Repeated thermal cycling (heating and cooling cycles) over years can weaken solder connections and cause micro-cracking. Ensure your panels have adequate airflow underneath—poor ventilation on low-slope roofs or flush-mount systems can worsen thermal stress. If you’re noticing gradual output decline year-over-year, thermal stress combined with normal degradation (0.3-0.8% annually) may be responsible.

Check for Inverter Clipping During Peak Production

Many residential solar systems are intentionally undersized on the AC side—the inverter is smaller than the combined DC capacity of all panels. This saves money but causes “clipping” on sunny days when panels try to produce more power than the inverter can handle. For example, a 10 kW panel array might connect to an 8 kW inverter. On peak production days, the inverter clips 2 kW of potential output.

If this was done deliberately by your installer to reduce costs, it’s not a malfunction—you’re getting the expected performance. Check your system specification sheet to see your panel-to-inverter ratio. A ratio above 1.25:1 (125% DC to AC) may cause noticeable clipping; a ratio of 1.0-1.25 is typical. If you believe you were undersized without discussion, ask your installer to run production simulations using PVWatts or Aurora Solar to show the expected annual output.

Examine the AC Breaker and Disconnect Switch

Between your inverter and the main electrical panel, there’s an AC disconnect switch and breaker. If either has tripped (switched to the OFF position), your entire system is offline. Check the main solar disconnect near the inverter—it should be in the ON position. Also check your main home electrical panel for a tripped circuit breaker labeled “solar.” Reset any tripped breaker by switching it fully OFF and then back ON.

Breakers trip for a reason—usually a ground fault or overvoltage event. If your breaker keeps tripping, stop attempting resets and contact your installer. Repeated trips indicate an electrical problem that requires professional diagnosis. Do not ignore or work around a tripped breaker, as this creates serious fire and safety risks.

Monitor Ambient Temperature Effects

In extremely cold climates, solar output can actually be quite good because panels operate more efficiently at lower temperatures. However, snow coverage will block output entirely. If your system is in a climate with frequent heavy snow, position panels at a steeper tilt angle (35-45 degrees instead of roof pitch) to encourage snow shedding. Some homeowners invest in panel heaters or heated racking in extreme climates, though cost-benefit is poor in most locations.

Heavy frost in the morning can cause temporary output loss as well. This is temporary and will resolve as the sun warms the panels. No action is needed. However, if you notice persistent frost or ice buildup on panels months after installation, you may have poor system ventilation—ensure adequate airflow under your array.

Request a Professional IV Curve Test

If your inverter is working, no obvious shading or damage is visible, and voltage readings seem normal, but output is still low, request a professional I-V (current-voltage) curve test from your installer. This test uses specialized equipment to measure the current and voltage output of each panel or string under real sunlight conditions. It will reveal hidden issues like internal cell degradation, bypass diode failure, or hot spots that aren’t visible to the naked eye.

An I-V tracer is a $2,000-5,000 instrument, so this service typically costs $200-500 depending on system size. If your system is under warranty and shows unexplained output loss, many installers will perform this test at no charge. The results are diagnostic gold—they pinpoint exactly which panel or section is underperforming.

Track Production Data Over Time

Most inverters log daily and monthly production data. Compare your current month’s output to the same month from previous years. Typical annual degradation is 0.3-0.8%, so you should expect about 0.3% less output each year. A steeper decline (more than 1% per year) suggests active problems. Seasonal variation is normal—summer produces more than winter in most climates. Compare apples-to-apples: this June to last June, not June to January.

If your system includes a monitoring app or website, use it to spot-check daily generation. A sudden drop from 25 kWh one day to 10 kWh the next (with similar weather) signals a problem. Take photos of the performance graph and send them to your installer—this data helps them diagnose issues remotely.

When to Call a Professional

Contact your installer immediately if you observe:

  • Inverter fault codes that don’t clear after 30 minutes
  • Physical damage to panels, wiring, or racking (dents, cracks, burn marks)
  • No output on a clear sunny day with no visible shading
  • Breakers that keep tripping
  • Signs of water intrusion in junction boxes or inverter housing
  • Burning smell or smoke
  • Output decline of more than 5% year-over-year

A service call typically costs $75-150 for diagnostics plus parts and labor for repairs. Most common repairs—replacing a breaker, re-seating a connector, or cleaning panels—run $200-600. Inverter replacement runs $2,000-4,000 including labor, but is usually covered under warranty if your system is relatively new.

Frequently Asked Questions

How often should I clean my solar panels?

In most US climates with regular rainfall, panels stay reasonably clean without manual intervention. However, if you live in a dusty, arid, or coastal area (salt spray), quarterly cleaning will optimize output. After dust storms or periods of heavy pollen, a cleaning within days will help. Monthly cleaning in desert climates or near farming areas can boost annual output by 3-7%.

Can I fix a tripped inverter breaker myself?

You can reset a breaker once by switching it fully OFF then back ON. If it trips again immediately, stop attempting resets and call your installer. Repeated tripping indicates a fault that needs professional investigation. Working around a tripped breaker creates electrocution and fire risks.

What is a hot spot on a solar panel?

A hot spot is a localized area of overheating on a panel, usually caused by a defect in one or more cells or a bypass diode failure. Hot spots can be detected with thermal imaging and are often covered under warranty. Thermography (thermal imaging surveys) can diagnose hot spots across your entire array for $300-800 depending on system size.

How long do solar inverters last?

String inverters typically last 10-15 years. Microinverters are rated for 25+ years. If your inverter reaches end of life, expect to budget $2,000-4,000 for a replacement including installation. Most failures occur between years 8-12, so plan for a potential replacement during your system’s second decade.

Can I use my phone’s camera to detect panel problems?

Some phone cameras can detect infrared light, allowing you to see hot spots or moisture in junction boxes, but the image quality is poor. Professional thermal imaging with calibrated equipment is far more reliable for diagnosing panel-level problems. If you suspect hot spots, contact your installer for a professional thermography survey.

Is a 1% annual output decline normal?

Typical annual degradation for modern panels is 0.3-0.8%, usually declining fastest in year one (0.8%) and then leveling off around 0.5% per year. If you’re seeing more than 1% annual decline, investigate for shading changes, inverter issues, or soiling buildup. Do not dismiss consistent 1%+ declines as normal—this suggests an active problem.

Summing Up

Most solar panel problems stem from a few common sources: inverter faults, shading, soiling, loose wiring, or degradation over time. Start your diagnosis by checking the inverter status lights, looking for new shading, and reviewing your production data. If visual inspection and simple tests don’t reveal the problem, a professional inspection with IV curve testing or thermal imaging will pinpoint the issue. The good news is that modern systems are remarkably reliable—the vast majority of residential arrays produce at or near warranty performance for 25+ years.

If your system is experiencing problems or you’re ready to install solar panels on your home, call Solar Panels Network USA at (855) 427-0058 or visit https://us.solarpanelsnetwork.com/ for a free consultation. Our solar experts can diagnose existing problems or design a new system tailored to your home and budget. The 30% federal Investment Tax Credit is active through 2032, making solar more affordable than ever.

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