Going solar is a big decision. Once the panels are up, most systems run quietly for years without much attention. But things do go wrong — output drops, inverters throw errors, batteries stop holding a charge. Knowing how to track down these problems can save you money and keep your system running the way it should.
This guide covers the basics: what to check yourself, when to call someone, and how to make sense of what your monitoring app is telling you.
How PV systems work
A photovoltaic system turns sunlight into electricity. That's the short version. The slightly longer version: solar cells in your panels absorb photons, which knock electrons loose. The cell's internal electric field pushes those electrons along, creating direct current (DC). An inverter then converts that DC into alternating current (AC) — the kind your house actually uses.
Your system is more than just panels on a roof. It's a few different parts working together, and a problem in any one of them can drag down the whole thing.
The main components
Most residential and commercial setups share the same basic parts:
Solar panels — capture sunlight, produce DC electricity. Mounted on your roof or a ground rack.
Inverter — converts DC from the panels into AC for your home. This is the piece most likely to need attention over the life of the system.
Battery storage — optional for grid-tied systems. Stores extra power for nighttime, cloudy days, or outages.
If something's wrong with your system, one of these three is usually involved.
Three types of systems
Not all solar setups work the same way:
Grid-tied — the most common type for homes. You're connected to the utility grid, so you can pull power when your panels aren't producing enough and send excess back.
Off-grid — completely independent from the utility. You need a battery bank, and usually a backup generator for stretches of low sunlight.
Hybrid — connected to the grid but also has battery storage, managed by . Gives you backup power during outages.
The type you have affects what can go wrong and how you troubleshoot it.
How to approach diagnosis
When your system isn't performing well, don't guess. Work through it methodically — start simple, then go deeper if needed. A lot of problems can be spotted without any special tools.
Visual inspection comes first
Before you touch a multimeter or call a technician, just look. Walk around and check for:
Debris and dirt — leaves, dust, bird droppings on the panels.
Physical damage — cracks, discoloration, warped frames, loose wires.
New shading — tree branches that have grown, new construction nearby, anything casting shadows that wasn't there before.
This takes five minutes and catches a surprising number of issues.
Electrical testing when visuals aren't enough
If everything looks fine but output is still low, electrical testing is the next step. This usually means measuring voltage and current to see if components are performing within spec.
One particularly useful test is I-V (current-voltage) curve analysis. It plots a panel's actual performance against what the manufacturer says it should produce under the same conditions. The gap between the two curves tells you a lot — degradation, mismatched modules, high-resistance connections.
Test parameter What it tells you What a bad reading means Open-circuit voltage (Voc) Maximum voltage with no load Low reading → faulty panel or bad connection Short-circuit current (Isc) Maximum current when shorted Low reading → soiling, shading, or cell defects
Thermal imaging
An infrared camera reveals temperature differences across your panels that you can't see with your eyes. Healthy cells should be roughly the same temperature. Hot spots — bright areas in a thermal image — are a red flag. They usually mean cracked cells, bad connections, or internal shorts.
Catching hot spots early matters. Left alone, they get worse, wasting power and eventually causing permanent cell damage. Most professional maintenance packages include a thermal scan for this reason.
What your monitoring data is telling you
If your system has monitoring software (most do), it's collecting a lot of data. Use it. Track your energy production over a few months and you'll start to see what "normal" looks like for your setup. When something goes wrong, that baseline makes it much easier to spot the problem.
Patterns worth watching:
Sudden sharp drops — often means the system shut down, the grid went out, or the inverter threw a fault.
Gradual, consistent underperformance — could be soiling, degradation, or a design problem from the start.
A sudden drop across the whole system usually points to the inverter. A slow decline in just one panel points to that panel or its wiring.
Why output drops over time
All solar panels lose some output as they age — that's normal. Most modern panels guarantee at least 85% of rated power after 25 years — some premium models go as high as 92%. Even older warranties covered a minimum of 80%. What you need to watch for is output dropping faster than expected.
Performance ratio
The performance ratio (PR) compares what your system actually produces versus what it theoretically could produce given the sunlight it receives. A PR of 0.80 means you're getting 80% of the possible output — accounting for shading, dirt, heat, wiring losses, and inverter efficiency.
If your PR starts falling over time, something beyond normal aging is going on.
Finding the actual cause
When output drops, start with the obvious stuff:
Has it been unusually cloudy? Not much you can do about that.
Are the panels dirty? Clean them and see if output recovers.
Any new shade? Check for tree growth or new obstructions.
If those don't explain it, dig deeper:
Inverter problems — the inverter handles all the power from your array. A fault here affects everything.
Panel or string-level faults — cell degradation, damage, or loose connections can take out a single panel or a whole string.
Environmental stress
Your system sits outside 24/7, year after year. It deals with heat, cold, rain, wind, hail, dust, pollen, and bird droppings. The panels are built for this, but there are limits.
Heat actually reduces panel efficiency — a hot panel produces less than a cool one. Humidity can accelerate corrosion over time, though modern panels are designed to be weather-resistant. Dust and pollen block sunlight. Hail can crack glass. These aren't hypothetical problems; they're the most common reasons for gradual performance decline.
PV array problems
The array — all your panels together — is the power-generating part of the system. When something's wrong, this is often where the problem lives.
Hot spots and cell degradation
A hot spot is a small area on a panel that runs much hotter than the rest. It happens when a cell or part of a cell has higher resistance, so energy gets converted to heat instead of electricity. Causes include manufacturing defects, micro-cracks, and mismatched cells.
Hot spots are bad news. They accelerate degradation, reduce output, and in extreme cases can be a fire risk. You can't see them without an infrared camera, which is why thermal scanning is part of any serious maintenance routine.
Soiling and surface contamination
Dust, dirt, pollen, bird droppings — this stuff builds up on your panels and blocks sunlight. It sounds trivial, but studies have found soiling can cut output by 5% to 15%, sometimes more in dry climates.
Rain helps, but it doesn't always get everything. In dry or dusty areas, you'll need to clean the panels yourself or hire someone to do it. A hose rinse works for light buildup. For stubborn grime, use a soft brush and deionized water (tap water leaves mineral deposits).
Mechanical damage: cracks, delamination, corrosion
Panels are tough, but hail, falling debris, and rough handling during installation can cause real damage. The main types:
Cracks — visible cracks in the glass are obvious. Micro-cracks in the cells are invisible without specialized equipment.
Delamination — the panel's layers start separating. Look for bubbling or peeling on the surface.
Corrosion — rust or degradation on the metal frame and junction box.
Some of these can be spotted visually. Repair almost always requires a professional.
Ground faults
A ground fault happens when a current-carrying conductor comes into contact with ground — often due to damaged insulation, water intrusion, or corroded wiring. Most inverters will detect this and shut down with a ground fault error code. If you see this repeatedly, call a technician. Ground faults can be a safety hazard and should not be ignored.
Shading, tilt, and orientation
Where your panels sit and how they're angled makes a big difference. In the Northern Hemisphere, facing panels toward true south at a tilt angle close to your latitude is generally ideal for maximizing annual production. Exact optimal angles vary with local climate. Even a small amount of shade on one panel can drag down an entire string in systems without panel-level optimization.
If you're getting less output than expected, check whether anything is casting new shadows — trees, chimneys, neighboring buildings. Systems using or DC optimizers handle shade better than traditional string inverters because each panel operates independently.
Inverter problems
The inverter is the component most likely to need repair or replacement over the life of your system. It converts DC from the panels into AC for your home, and it does a lot of complex work in the process.
Fault codes
When the inverter detects a problem, it usually shuts down and displays an error code — on the unit itself or in your monitoring app. Each manufacturer has different codes, so you'll need your manual to decode them.
Common codes relate to grid voltage or frequency being out of range, internal overheating, or communication failures with the panel array. Some are temporary (a brief grid fluctuation) and the inverter restarts on its own. Others mean something is actually broken.
Grid synchronization and anti-islanding
Grid-tied inverters must sync their output with the utility grid's voltage and frequency. If the grid goes down, the inverter must shut off immediately — a safety feature called anti-islanding. Without it, your system could send power into the grid while utility workers are trying to fix the outage, which is dangerous.
Two common problems:
Frequent disconnections — usually means grid voltage or frequency in your area is unstable.
Failure to reconnect after an outage — could be a fault in the inverter's grid-sensing circuitry.
MPPT failures
Maximum Power Point Tracking (MPPT) is what lets the inverter squeeze the most power out of your panels as sunlight conditions change throughout the day — it's the more advanced of . If the MPPT controller fails or gets stuck at the wrong voltage, your system won't produce as much as it should — even in full sun.
Signs of MPPT trouble: output that's lower than expected for the weather, or output that fluctuates erratically when sunlight is steady.
Diagnosing MPPT issues usually requires a technician to analyze the inverter's performance data. But if you notice a sustained, unexplained drop in output, that's worth investigating.
DC-AC conversion faults
The inverter's main job is converting DC to AC. The power electronics inside that make this happen — capacitors, transistors, and so on — have finite lifespans. Heat, voltage spikes, and age all contribute to eventual failure.
When these components fail, the inverter might not turn on, might shut down under load, or might produce unstable AC output. Because of the high voltages involved, this is not something to fix yourself. Call a technician.
Battery storage problems
If you have a hybrid or off-grid system, your battery is what keeps the lights on when the sun isn't shining. Batteries are more reliable than they used to be, but they're still the most maintenance-intensive part of a solar system.
Capacity fade
All batteries lose capacity over time. That's just chemistry. How fast depends on how many charge-discharge cycles they go through, how deeply you discharge them, and the temperature they operate at. Running a battery to empty regularly or cooking it in a hot garage will age it faster.
Watch for:
Shorter backup runtime — the battery doesn't last as long as it used to on a full charge.
Monitoring alerts — most systems track battery health and will warn you when capacity has dropped significantly.
Charging and discharging faults
If the battery isn't charging, the problem might not be the battery. It could be the panels (dirty, underproducing), the (showing errors), or the wiring. If the battery won't discharge, check the inverter, look for tripped breakers, and see if the battery management system (BMS) has flagged a safety issue.
BMS failures
The Battery Management System monitors cell health, manages charging, and prevents the battery from operating outside safe limits. If the BMS fails, the battery might refuse to charge or discharge even though the cells are fine. It might also give inaccurate readings.
Signs: communication errors between the BMS and inverter, or shutdowns that don't seem justified. Because the BMS is a safety device, any suspected failure should be checked by a professional.
Thermal runaway
This is the worst-case scenario for lithium-ion batteries. A chain reaction where rising temperature causes further temperature rise, potentially leading to fire. It's rare but serious.
Causes include internal shorts, overcharging, physical damage, and manufacturing defects. Modern systems have multiple safeguards — temperature sensors, automatic shutdown, cell-level monitoring — but they're not foolproof. Buy certified batteries from reputable manufacturers and have them installed by a professional in a well-ventilated location.
Using your monitoring data
Most modern systems come with a monitoring app or web portal connected to the inverter. It shows real-time production and historical data. Use it. It's the easiest way to catch problems early.
What to look at
Real-time output — a quick check tells you if the system is running right now.
Daily and monthly trends — compare against the estimates from your original solar proposal.
Alerts — many systems send automatic notifications when something goes wrong.
Performance ratio and energy yield
Energy yield is how much electricity your system actually produces. Performance ratio (PR) compares that against what it theoretically could produce given the sunlight available. A dropping PR over time suggests something beyond normal aging is going on.
Benchmarking against expectations
Your original solar proposal included an estimate of annual production based on your location, system size, and equipment. Compare your actual output to those estimates. A consistent, significant gap could mean a design problem, an equipment fault, or new shading.
Remember that production varies seasonally. Compare month-to-month against the same month last year, not against last month.
Predictive maintenance
The best monitoring setups don't just tell you what happened — they help you see what's coming. Small, steady declines in a single string's output might mean corrosion or early cell degradation, long before it causes a total failure. Catching these early means cheaper repairs and less downtime.
Preventive maintenance
Solar systems are low maintenance, not zero maintenance. A little regular attention prevents expensive problems later.
What you can do yourself
Quarterly or semi-annual visual checks — walk around, look for debris, dirt, and obvious damage.
Clean the panels when they're visibly dirty. How often depends on your climate — rainy areas might need once or twice a year, dusty areas more often.
Trim tree branches that are starting to cast shade.
Keep a log of inspections and any maintenance performed. It helps with troubleshooting later.
When to call a professional
Annual inspection by a certified PV technician — they'll check electrical connections, inverter performance, and mounting integrity. Between visits, following helps prevent avoidable failures.
Any inverter fault codes you can't resolve yourself.
Electrical issues — tripped breakers, suspected wiring problems.
Anything requiring I-V curve tracing, thermal imaging, or opening up equipment.
Don't try to fix electrical problems yourself. It's dangerous and may void your warranties.
FAQs
How long do PV systems last?
Panels are typically warrantied for 25 to 30 years and keep producing after that, though at lower output. String inverters typically need replacement after 10–15 years. Microinverters last longer, often 20–25 years or more, and usually come with 25-year warranties. With decent maintenance, a system can provide power for 30+ years.
What incentives support solar adoption?
In the US, the federal solar Investment Tax Credit (ITC) is the primary incentive — it currently covers 30% of installation costs (through 2032 under the Inflation Reduction Act). Many states also have net metering programs and solar rights provisions. Other countries have their own incentive structures. These change over time, so check what's currently available in your area. If you're still planning your installation, strategically can help you lock in the best available incentives.