Common Solar Panel Problems in Northern Ireland and How to Fix Them

Solar Panel Problems Are Rare, But They Do Happen

Solar panels are remarkably reliable. With no moving parts and a design life of 25 years or more, most systems run for years without any issues at all. But “low maintenance” does not mean “zero problems,” and when something does go wrong, it helps to know what you are dealing with.

This guide covers the most common solar panel problems reported by homeowners in Northern Ireland, how to diagnose them, and whether you can fix them yourself or need to call a professional.

Low Output: The Most Common Complaint

The single most frequent concern homeowners raise is that their panels are not producing as much electricity as they expected. Before assuming there is a fault, it is worth understanding what “normal” looks like.

Seasonal Variation

In Northern Ireland, solar output varies dramatically by season. A system that generates 15 to 20 kWh per day in June might produce just 2 to 4 kWh per day in December. This is entirely normal. NI receives around 900 to 1,100 kWh of solar irradiance per square metre per year, but most of that arrives between April and September.

If your system seems low in winter, compare it to the same period last year rather than to summer figures. A 10 to 20% variation from the installer’s original estimates is within normal range, as those estimates are based on long-term averages.

Shading

Shading is one of the most common causes of underperformance, and it can creep up on you. A tree that was small when your panels were installed may have grown enough to cast a shadow across one or more panels during parts of the day. Even partial shading on a single panel can significantly reduce the output of an entire string if your system uses a traditional string inverter.

Walk around your property at different times of day and check for new shading sources: tree growth, a neighbour’s extension, a new aerial or satellite dish, or even a build-up of moss on the roof above the panels.

Dirty Panels

Northern Ireland’s frequent rainfall does a good job of keeping panels clean, but bird droppings, tree sap, and lichen can accumulate in spots that rain does not wash away. A heavy layer of grime can reduce output by 5% or more. Panels at a low tilt angle (below 15 degrees) are particularly susceptible, as water pools rather than running off.

Inverter Faults

The inverter is the hardest-working component in your solar system, and it is the part most likely to develop problems during the system’s lifetime.

Common Inverter Issues

• Error codes on the display. Most inverters have a small screen or LED indicators. If you see a red light or an error code, note it down and check the manufacturer’s manual or website. Many error codes relate to grid voltage fluctuations, which are temporary and resolve themselves.
• Zero generation during daylight. If your monitoring app shows no output during clear daylight hours, the inverter may have tripped or failed. Check that it has not simply been switched off at the isolator. If the isolator is on and the display is blank or showing an error, contact your installer.
• Intermittent shutdowns. If the inverter restarts itself frequently, this can indicate a grid voltage issue, an internal fault, or overheating. Inverters installed in hot, unventilated spaces (such as an enclosed loft) may shut down on warm days to protect themselves.

Inverter Lifespan

String inverters typically last 10 to 15 years, so if your system is approaching that age, an inverter replacement may be on the horizon. Budget £800 to £1,500 for a replacement, depending on the type and capacity. Microinverters (mounted behind each panel) tend to last longer, often 20 to 25 years.

Hot Spots

Hot spots occur when one cell within a panel generates heat instead of electricity. This can happen due to a manufacturing defect, a micro-crack, or persistent localised shading (such as a bird dropping that has baked on).

You may notice a hot spot as a discoloured or browned area on the panel surface. In some cases, you can feel the heat difference by hovering your hand near the panel (do not touch it). Hot spots reduce output and, if severe, can damage the panel’s encapsulant layer over time.

If you suspect a hot spot, contact your installer. They can use a thermal imaging camera to confirm the diagnosis. Hot spots on panels still under warranty should be covered by the manufacturer’s product warranty.

Micro-Cracks

Micro-cracks are tiny fractures in the silicon cells that are invisible to the naked eye. They can be caused by thermal cycling (repeated heating and cooling), physical impact, or poor handling during installation. Over time, micro-cracks can grow and cause cells to disconnect, reducing the panel’s output.

Micro-cracks are diagnosed using electroluminescence (EL) testing, which requires specialist equipment. If your system shows a gradual, unexplained decline in output that is not related to shading, dirt, or the inverter, micro-cracks may be the cause.

Bird and Pigeon Damage

Pigeons in particular love the warm, sheltered space beneath solar panels. Once they move in, they bring a host of problems:

• Nesting material can block ventilation, causing panels to overheat and reduce output.
• Droppings are acidic and can etch the panel surface if left to build up. Heavy droppings on a single panel also act as shading, reducing output disproportionately.
• Gutter blockages from nesting debris can cause water damage to your roof and fascia.

If you have a pigeon problem, bird-proofing mesh fitted around the edges of your panels is the most effective long-term solution. Removing existing nests first (outside of nesting season, to comply with wildlife legislation) and then fitting mesh prevents them from returning.

Water Ingress

Water ingress into the panel’s junction box or into the wiring connections can cause corrosion, earth faults, and potentially dangerous short circuits. Signs of water ingress include:

• Condensation visible inside the panel glass (a small amount can be normal, but persistent fogging is a concern)
• Tripped RCD or earth fault warnings on the inverter
• Visible corrosion or green discolouration on connectors

Water ingress is more common in coastal parts of Northern Ireland, where salt-laden air accelerates corrosion. If you live on the coast or within a few miles of it, annual visual checks of cable connections and junction boxes are particularly worthwhile.

Loose Connections and Wiring Issues

Poorly crimped MC4 connectors, cables that have worked loose in the wind, or rodent damage to exposed wiring can all cause intermittent faults. These issues often show up as unexplained drops in output that come and go.

Check from ground level that all visible cables are still neatly secured and not hanging loose. If cables are accessible, look for signs of damage: chewing marks, cracked insulation, or discoloured connectors. Do not attempt to repair or reconnect wiring yourself. DC wiring on solar panels carries a significant electrical risk and must be handled by a qualified professional.

NI-Specific Issues

Northern Ireland’s climate and geography present a few specific challenges:

• Wind damage. NI is one of the windiest parts of the UK. After any significant storm, do a visual check for shifted panels, lifted edges, or displaced mounting clips. Coastal properties are most at risk.
• Salt air. Properties within a few miles of the coast may experience accelerated corrosion on metal mounting components and connectors. Stainless steel or marine-grade aluminium fixings help, but periodic checks are still advisable.
• Heavy rainfall. While rain keeps panels clean, persistent heavy rain can occasionally overwhelm seals on older junction boxes. Systems over 10 years old in high-rainfall areas deserve closer attention.

When to DIY vs When to Call a Professional

You can handle:

• Visual inspections from ground level
• Checking your monitoring app for output patterns
• Noting down inverter error codes
• Cleaning accessible panels with a soft brush and water
• Clearing gutters of debris from bird nesting

Call a professional for:

• Any work involving electrical connections or DC wiring
• Inverter fault diagnosis and replacement
• Hot spot investigation (requires thermal imaging)
• Bird proofing installation at height
• Any issue where you would need to go on the roof
• Persistent unexplained output drops that you cannot attribute to weather or shading

Most reputable NI solar installers offer maintenance and diagnostic services. If your original installer is no longer trading, any MCS-certified installer can assess your system. Expect to pay £100 to £200 for a diagnostic visit.

Keep Monitoring, Catch Problems Early

The single best thing you can do to catch problems early is to keep an eye on your monitoring data. Whether you use the inverter manufacturer’s app, a third-party monitoring system, or simply note down your generation meter reading each month, having a record of your system’s output makes it far easier to spot when something has changed. A sudden drop suggests a fault; a gradual decline might be normal degradation or a slowly growing shading issue.

Most problems with solar panels are straightforward to fix once diagnosed. The key is catching them early, before a small issue becomes a costly one.