Solar Panel Problems Solved

Solar panels are incredibly reliable, but like any technology exposed to the elements, they can occasionally develop problems. The good news is that most common issues are easily diagnosed and fixed. Whether it’s a drop in generation, visible damage, electrical faults, or environmental issues, understanding what can go wrong helps you act quickly and protect your investment.

In this guide, we’ll walk through the most common solar panel problems UK homeowners encounter, explain what causes each issue, and describe how to fix or prevent them. We’ll also cover when you need a professional and when a simple reset might solve the problem.

The key to getting the most from your solar panels is regular monitoring and maintenance. If you notice a sudden drop in generation or visible damage to your system, don’t ignore it. Early action can prevent minor issues from becoming expensive repairs.

Key Takeaways

• The most common solar panel problems are shading (trees, buildings, dirt), inverter faults, and generation drops due to weathering
• Many inverter issues can be resolved by restarting the inverter (switch it off for 30 seconds and back on)
• Delamination (white spots or bubbling on the panel) indicates moisture ingress and requires professional repair or replacement
• Hotspots (localised overheating within the panel) are rare but serious and require immediate attention to prevent panel damage
• Bird netting and gutter guards can prevent bird damage and nesting beneath panels
• Most panels can be cleaned with soft brushes and deionised water, but this rarely boosts generation by more than 2 to 5%
• Cracked glass on a single panel may be repairable if the crack is small, but severely damaged panels should be replaced
• Annual professional inspections can catch problems early and optimise system performance

Problem 1: Sudden Drop in Generation

A sudden drop in electricity generation is the most obvious sign that something is wrong. If your inverter display or monitoring app shows significantly lower output than usual for the time of year, investigate immediately.

First, rule out the obvious: check the weather. Heavy cloud cover, rain, or snow will reduce output. If the weather is clear and output is still low, move to the next steps.

Second, check your inverter. Look at the LED display or your monitoring app. If the inverter is showing an error code or is in standby mode, there may be an electrical fault. Write down the error code and contact your installer or a qualified solar engineer.

Third, visually inspect your panels for obvious damage: shattered glass, large cracks, or visible delamination (white spots or bubbling). If you see damage, stop using the system and call a professional to assess safety.

Fourth, check for shading. New trees, hedges, or nearby construction can cause shading. If a portion of your array is shaded, generation can drop by 20 to 30% because bypass diodes in the shaded panels reduce the output of the entire string. Trim trees if possible, or discuss shading solutions with your installer.

Finally, if none of these issues apply, your installer should perform a full system test using a thermal camera to check for hotspots and test electrical continuity in the wiring.

Problem 2: Inverter Faults and Error Codes

Your inverter is the “brain” of your solar system, converting DC electricity from the panels into AC electricity for your home and the grid. Inverter faults are the second-most common solar problem.

Many inverter errors can be resolved by a simple restart. Switch off the DC isolator (between the panels and inverter) and the AC isolator (between the inverter and grid), wait 30 seconds, and switch both back on. The inverter will take a few minutes to restart and perform self-tests. If it restarts normally, the error may have been a temporary glitch.

Common error codes include “Grid Fault” (the inverter has lost connection to the grid or detected a grid voltage anomaly), “Temperature Warning” (the inverter is running hot and has throttled output), “String Fault” (broken wiring or a panel failure in one of the strings), and “Isolation Fault” (a short circuit or leakage in the DC wiring).

If the error code persists after a restart, contact your installer. Some error codes indicate a serious fault that requires professional diagnosis. Never attempt to repair an inverter yourself: they contain high voltage components that can cause electrocution.

Most inverter warranties cover repairs or replacement for 5 to 10 years. If your system is within warranty and an inverter fails, your installer should replace it free of charge.

Problem 3: Delamination and Moisture Ingress

Delamination is one of the most serious long-term panel problems. It appears as white spots, bubbling, or hazing on the surface of the panel, usually near the edges or bottom. Delamination indicates that moisture has entered the panel and the EVA encapsulation (the plastic layer that binds the glass to the silicon cells) has deteriorated.

Delamination can happen for several reasons: manufacturing defects (poor EVA curing), edge seal failure (the gasket around the frame has failed), long-term UV degradation of the EVA, or thermal cycling stress. Once moisture is inside the panel, it can corrode the silicon cells, the metal contacts, and the wiring, gradually reducing the panel’s output.

If you notice delamination, monitor the panel’s output. Minor delamination may not affect generation significantly. However, if the affected area is large or spreading, or if generation is dropping, the panel should be replaced. Delamination usually develops over years and is a slow process, but once started, it will continue.

Prevention is the best approach. Ensure your panels are installed with high-quality edge seals and gaskets, avoid panels with thin backsheets, and have your system inspected annually for signs of moisture ingress.

If your panel is within warranty (usually 25 to 30 years), delamination may be covered. Contact the manufacturer with photos of the affected area and the panel’s serial number. Many manufacturers will replace delaminated panels even after many years of use.

Problem 4: Hotspots

Hotspots are localised areas of extreme heat within a solar panel, usually caused by a defective cell or shading across part of a cell. A hotspot can reach temperatures of 80 to 100 degrees Celsius or higher, which is much hotter than the panel’s normal operating temperature (30 to 50 degrees Celsius under sunlight).

Hotspots are dangerous because they accelerate degradation of the EVA encapsulation and backsheet, leading to premature failure. In rare cases, a hotspot can cause a cell to crack or the panel to catch fire if the current bypass diode fails.

You cannot see a hotspot with your naked eye, but they can be detected using a thermal imaging camera. If your installer suspects a hotspot (often based on a sudden and significant drop in a single panel’s output), they will use thermal imaging to confirm.

If a hotspot is detected, the affected panel should be replaced. Hotspots are usually caused by manufacturing defects or internal cell damage, not installation or environmental issues, so they may be covered under the panel’s manufacturing warranty.

Prevention: choose high-quality panels from reputable manufacturers. Some premium brands use cell-level bypass diodes (one diode per cell instead of one per string) to prevent hotspots entirely.

Problem 5: Cracked Glass and Physical Damage

Cracked or broken panel glass can result from hail, impact from objects (tree branches, roof debris), or thermal shock (sudden temperature change). A small crack may not immediately affect performance, but it allows moisture to enter the panel, which will eventually cause failure.

If you see a small crack (hairline, less than 10cm long) that does not go through the full thickness of the glass, monitor the panel but plan for eventual replacement. If the crack is large (more than 10cm), goes through the full thickness, or the glass is shattered, the panel should be replaced immediately to prevent further water ingress.

Replacing a single panel is possible but requires technical skill. Your installer will disconnect the panel (and possibly the entire string), remove the damaged panel from its mounting, and install a replacement. The cost is typically £400 to £600 per panel including labour, plus the cost of the replacement panel (£200 to £350 for a standard 400W panel).

Prevention is key. Ensure your installation includes adequate clearance for tree branches, trim overhanging trees regularly, and if you live in an area prone to severe weather, discuss hail-resistant mounting systems with your installer.

Problem 6: Wiring and Connection Issues

Loose wiring, corroded connections, or damaged connectors can cause intermittent generation loss or electrical faults. Wiring issues are difficult for non-professionals to diagnose because they may not create obvious signs.

If your system exhibits intermittent faults (generation is normal some days but low on others, or the inverter shows connection errors), your installer should inspect all wiring and connectors for corrosion, loose bolts, or damage.

Corroded connections are common in coastal areas where salt spray accelerates oxidation. The fix is to disconnect the affected connector, clean the contacts with a soft brush and contact cleaner, and reconnect. Heavily corroded connectors may need replacement.

Loose MC4 connectors (the standard connectors on panels) can be tightened, but they should never be disconnected and reconnected unnecessarily. Each time a connector is disconnected, it risks damage. If a connector is faulty, it should be cut out and replaced with a new connector, not reused.

This is a job for a qualified solar engineer. Attempting to fix electrical connections without training risks electric shock or damage to the system.

Problem 7: Bird Damage and Nesting

Birds nesting beneath solar panels or pecking at the backsheet can cause damage. Pigeons, sparrows, and other birds sometimes nest in the gaps between panels and the roof, which can block ventilation and reduce cooling. More seriously, birds may peck at the backsheet, trying to access insects beneath the panels, creating holes that allow moisture and insects inside.

Bird damage is preventable with bird-proofing measures. Bird netting or mesh installed around the edges of your array prevents birds from entering the gap beneath the panels. The netting should be UV-resistant and installed professionally to ensure it does not interfere with airflow or create additional wind load on the structure.

Gutter guards and leaf screens also help prevent debris from blocking ventilation beneath the panels, which indirectly reduces bird nesting (they prefer sheltered gaps).

If birds have already caused damage (holes in the backsheet or visible pecking), the affected panel may need replacement if the damage is severe. If the damage is minor, your installer can assess whether it poses a risk before deciding on repair or replacement.

Problem 8: Dirt, Dust, and Soiling

Dirt, dust, bird droppings, and leaf debris accumulate on panel surfaces over time. Soiling can reduce generation by 2 to 5% on average, or more if the soiling is heavy or localized to a specific area.

Cleaning panels is straightforward: use a soft brush (not abrasive or stiff bristles that can scratch the glass) and deionised water. Avoid tap water, which may leave mineral deposits. In the UK’s climate, regular rain often cleans panels naturally, so annual cleaning is usually sufficient. In drier regions or after particularly dusty conditions, you may clean more frequently.

Do not use pressure washers or harsh chemicals on panels: they can damage the seals and glass coatings. Never walk on panels: the structural load can crack cells beneath the surface.

If you live near trees or areas with high dust, consider professional panel cleaning once per year. The cost (typically £200 to £400 for a residential system) is worthwhile if cleaning boosts generation by 3 to 5%, which can add £50 to £100 per year in extra electricity or feed-in revenue.

Many modern inverters can tell you how much cleaning would improve output. Check your monitoring app: if it shows “soiling loss” or similar, cleaning may provide a tangible boost.

Problem 9: Shading and Panel Orientation Issues

Shading is the most common environmental problem affecting solar panels. Trees growing taller over the years, new buildings casting shadows, or roof-mounted equipment (vents, aerials) can cast shadows on panels, reducing generation.

Partial shading of a single panel can reduce the output of the entire string by 15 to 30% if that panel has older bypass diodes. Modern panels with multiple bypass diodes are less sensitive to shading, but it still reduces output.

To diagnose shading problems, watch your array throughout the day and note when shadows fall on it. If shading is from a tree you own, trimming or removing the tree is the solution. If shading is from a neighbouring property, you may need to discuss the issue with your neighbour or contact your installer about adding another smaller array in an unshaded location.

In some cases, panels can be repositioned or the array split into multiple strings with separate inverters (called “microinverters” or “power optimisers”) to minimise shading impact. This is more expensive but can recover 10 to 20% of lost generation if shading is significant.

Case Study: Diagnosing and Solving Generation Loss in Yorkshire

Background

A homeowner in Yorkshire had owned a 5kW solar system for 8 years. The system had been consistently generating about 18 to 20 kWh per day in summer, but over the past 18 months, output had dropped to 12 to 15 kWh per day. The homeowner contacted their installer to investigate.

Project Overview

The installer visited and performed a visual inspection. The panels appeared clean and undamaged. The inverter was operating normally with no error codes. The first thing the installer noticed was that two large oak trees in the adjacent garden had grown significantly taller and were now casting shadows across the southern roof for about 4 hours each afternoon.

Implementation

The installer explained that the shading was causing the generation loss. Partial shading of one or two panels reduced the output of the entire string. The installer recommended trimming the trees on the neighbouring property (which would require the homeowner’s agreement with their neighbour) or installing micro-inverters on the affected panels to reduce shading impact. The homeowner agreed to approach the neighbour about tree trimming as the simpler solution.

Results

Once the trees were trimmed back, summer generation returned to 18 to 20 kWh per day. The homeowner learned a valuable lesson about monitoring shading over time and acting early. They also planned to have the trees monitored and trimmed every two to three years to prevent the issue recurring.

Expert Insights From Our Solar Panel Installers About Problem-Solving

One of our senior solar panel installers with over 16 years of experience says: “Most problems I see could be prevented or solved early with regular monitoring. Homeowners often don’t check their inverter display or monitoring app for weeks, so a small fault becomes a major generation loss. The first thing I always tell customers is to watch the inverter display daily or check the app. If the inverter shows an error code or generation suddenly drops, contact your installer immediately. Nine times out of ten, it’s a simple fix like a restart or checking for shading. But if left unchecked, a small problem can cause expensive damage.”

Frequently Asked Questions

Summing Up

Most solar panel problems can be prevented or solved quickly if you monitor your system regularly and act early. Watch your inverter display or monitoring app daily, watch for visual damage, and be aware of changes in your environment (new shading, debris, etc.). Many inverter faults can be resolved with a simple restart. For issues you cannot diagnose yourself such as delamination, hotspots, or electrical faults, contact your installer or a qualified solar engineer. Regular maintenance and professional inspections will help your system remain reliable and efficient for the full 25 to 30 year lifespan. For advice on diagnosing a specific problem or scheduling a professional inspection, contact us for a free quote.

Updated April 2026