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Solar panels are generally quite reliable. More than seven in 10 owners in our survey had never had a technical fault with their solar panel system. Some have owned their solar panels for a decade.
The most common – and most serious – problem owners face is with the inverter. In some cases inverter problems mean you don't get any usable renewable electricity.
It can also be a pricey problem to fix. But if you know about it, you can factor repair costs into your investment.
We surveyed 1,116 solar panel owners on our Which? Connect panel in June 2021 to find the most common technical faults with solar systems. Plus they told us about other issues that plague them, including pigeons and squirrels nesting under their solar panels. Keep reading to find out what you can do.
It's not surprising that the inverter is the most common part of the solar panel system that owners reported problems with. While solar panels have warranties for 20 or 25 years, inverters aren't expected to last as long.
You should expect to replace your inverter at some point during the life of your solar panels.
If your inverter isn't working, you won't be able to use the electricity generated by your solar panels, so it's important to get it fixed quickly.
If you have recently had a power cut, check that the solar PV breaker in your consumer unit is in the on or up position. If it trips to the off position, call an engineer; if it stays on, check the inverter for error messages.
Check if your inverter is still within its warranty. If so, contact the company about the fault. If not, contact your solar panel installer for professional advice on replacing it.
Find a reputable solar panel installer using Which? Trusted Traders. You can also use our Trusted Traders search tool below to find local solar panel experts in your area.
Other problems with solar panels
Though serious solar panel system faults are rare, owners reported having other issues with their solar PV systems including:
birds or squirrels nesting (15%)
dirt building up on the panels (14%)
shadows from trees or other buildings (7%)
loose or damaged roof tiles (3%).
Unlike many technical faults, these problems are often possible to solve yourself, or take steps to prevent happening in the first place.
If you're still choosing your solar panels, use our buying advice for solar PV to find the right system for your home.
Here we share their tips on identifying and solving the solar PV problems that owners told us were most common. Click on a problem to find out how to solve it.
Whenever you call a professional, make sure that they are registered with the Microgeneration Certification Scheme (MCS). This ensures that they’re signed up to deliver high standards and you have access to redress if something goes wrong.
Half of inverter problems are actually due to the solar array having a faulty panel or cable and the inverter detecting this, according to Bright Green Renewables managing director Mark Partridge. If the inverter is showing an error message, refer to the manual (or search online) to find out what it means.
Check that solar PV breaker in your consumer unit is in the on/up position, Ask Renewables advises. If it’s off (this can happen after a power cut), flick it on. If it trips to the off position again, call an engineer. If it stays on, check the inverter for error messages.
How urgently should I get it fixed?
Without the inverter, you won’t be able to use electricity generated by your solar panels. So you won’t benefit from free electricity, or the feed-in tariff (if you get it). If the inverter is off or in fault mode, it is generally safe, Ask Renewables explained.
Birds – or even squirrels – making their home under your solar panels is a pain, especially if they scratch them, damage the wiring or soil them.
You can buy plastic strips and attach them to the panels to help stop animals being able to squeeze underneath, Bright Green Renewables advises.
Or if you’re thinking of installing solar panels, consider roof-integrated panels. These can be complex to retrofit but are built into the roof, leaving no gaps for birds or rodents to get underneath them.
How urgently should I get it fixed?
Birds nesting under your panels is annoying, and can result in damage. But it’s less urgent an issue to tackle than other problems.
This might be caused by bird droppings, traffic pollution if you live in an urban area, or a build-up of salt if you live near the coast, Ask Renewables explains.
A heavy rain storm should usually be enough to wash off most dirt, it adds, although if you notice that it’s building up a lot then it could mean your panels generate less electricity than their potential.
How urgently should I get it fixed?
Unless the build-up of dirt is very thick, or a significant amount has accumulated on one panel (perhaps a pigeon sits on your TV aerial and its droppings fall onto one panel), it’s unlikely to cause a problem beyond a slight drop in generation. So it’s worth fixing but isn’t urgent.
These are generally rare, according to Bright Green Renewables. Indeed 6% of people in our survey had some sort of electrical problem.
These could be caused by various things, Ask Renewables explains, including faulty materials, poor workmanship, other electrical works at your home which have an impact, loose connections or a variable voltage coming into your home from the grid.
Additionally, the DC electrical cables that join the panels together can sometimes suffer from water getting into them or chafing on roof tiles, Bright Green Renewables told us.
How urgently should I get it fixed?
As soon as possible. Check the display on your inverter, as its error message (or code) could tell you the cause. Call a solar panel maintenance professional, rather than attempting to fix an electrical problem yourself.
The most likely cause of this rare problem is dirt build-up or weather conditions, both Trusted Trader companies agree.
Misty mornings will impact the generation of east-facing panels, in particular, Ask Renewables explains, while thick cloud will mean that your panels produce less electricity than on bright sunny days. Bright Green Renewables adds that some years are sunnier than others and this has an impact on how much electricity your panels will generate.
Secondary causes are dirt building up on your panels (see above for how to solve this), trees growing above your panels and shading them, or a problem with a connection or component behind a panel.
How urgently should I get it fixed?
Weather conditions are a fact of solar pv life and there’s nothing you can do about it. If you suspect there might be something else behind a drop in electrical production, Ask Renewables advises you take a good look at your panels and their surroundings to check for shade that might not have been present when your panels were installed.
This is generally caused by a fault with the inverter or a problem with the wiring, Bright Green Renewables explains. Occasionally the generation meter might fail. If this happens, you’d see no recorded generation, even though the system is working.
First check the solar pv breaker in your consumer unit, Ask Renewables recommends. It should be in the on/up position. If it’s in the off/down position (which can happen after a power cut) try to flick the switch back on. If it trips back to the off position, leave it off and call an engineer. Check your inverter for any fault codes or error messages.
How urgently should I get it fixed?
The longer you go without your panels producing electricity, the less renewable power you’ll use and the more you’ll have to buy from the grid. Plus if you receive the feed-in tariff, you won’t get paid while your panels are not producing electricity.
Generation meters can occasionally fail, though this is rare.
Bright Green Renewables advises checking the real-time and cumulative generation on your inverter (most have these options) to check that the solar panels are still generating electricity. If the system is generating at the inverter then this implies a failed generation meter.
How urgently should I get it fixed?
If the fault is only with the generation meter, then the panels should still be generating and feeding electricity to the property, Ask Renewables explains. But if you’re claiming the feed-in tariff, then you won’t be able to take meter readings (required to calculate your payments). So it’s worth calling a professional to get this fixed.
Neither Which? Trusted Trader has come across this problem, backing up our survey finding that it’s very rare.
But if you suspect this might be the case, Bright Green Renewables suggests checking your inverter, as it also records generation levels. Compare the readings over a few days to establish whether the main generation meter is accurate.
How urgently should I get it fixed?
If you believe that your generation meter is inaccurate, it could impact the meter readings you give to your supplier if you claim the feed-in tariff. So it’s worth calling a professional to get this fixed.
You should have two isolators: one at the inverter and one close to the consumer unit. A problem could be caused by loose internal connections. Your inverter will show an error if this is the case, and the code it displays should help identify if the fault is on the AC or DC side, Bright Green Renewables explained.
If you suspect an isolator problem, follow the shut-down procedure that should have been left with you by your installer, Ask Renewables advises. If you don’t have one, turn off the PV breaker switch at the consumer unit.
How urgently should I get it fixed?
Urgently. You should get a qualified electrician to investigate the wiring and isolators. They will probably use the fault codes on your inverter to do this.
This rarely happens after installation, Bright Green Renewables says, and if it does it shouldn’t affect the output of the panel by much.
If you suspect it has happened, it would probably have been caused by an impact, Ask Renewables says. Solar panels from MCS-registered brands are made with tempered glass so will shatter rather than crack, like a car windscreen.
How urgently should I get it fixed?
Since the effect on electricity production is minimal, you have time to budget for a replacement panel (ideally matching in size, make and model) or see if you can get a replacement under warranty. You should get a professional to replace the panel.
