Solar panel problems and how to solve them

Solar panels are generally quite reliable. Many owners don't experience technical faults in over a decade of ownership.

Nearly seven in 10 owners had had no problems with their solar panels in our survey of over 2,000 owners.*

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 or replacement costs into your investment.

Here we run through some of the most common problems with solar panels. To get answers, we spoke to several Which? Trusted Traders and looked at guidance from industry body Solar Energy UK and standards body MCS.

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Solar panel inverter problems

Solar panels can have warranties of up to 20 or 25 years, but 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. 

Find out how much you should expect to pay for a new inverter and other tips to make the most of your solar panels.

If your inverter isn't working, you won't be able to use the electricity from your solar panels, so it's important to get it fixed quickly.

It might be due to loss of electrical (AC) supply, explains Ben Robinson, director of Exeo Energy Ltd. This could be caused by a lightning strike or power cut which has tripped the solar circuit trip switch. 

"The first port of call should be checking the distribution board or consumer unit to ensure that the solar circuit's trip switch is in the 'up' position. If not, pushing the trip switch up will resolve it," Mr Robinson explains. 

If your inverter has a display showing an error code, check your manual or search online to find out what it means. 

It's also possible that the DC power from the solar panels has been lost, explains Mr Robinson. This could be caused by the DC rotary isolator being switched off, connectors from positive and negative cables being disconnected or the DC cables severed. 

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.

Solar panel electrical problems

Faulty electrical connections or wiring could be caused by:

• loose connections
• wear and tear (by insufficiently-secured wires chafing on roof tiles)
• poor workmanship or other electrical works since your solar panel installation impacting on them

That's according to the Which? Trusted Traders we spoke to.

"Never (unless qualified) interfere with connections or wiring, as there's a serious risk of electric shock" warns Steven Cant from Which? Trusted Trader Sun Smart UK. 

Instead, "if it's safe, turn the DC and AC isolators to the off position and call your installer or a qualified electrician".

If your system is still within warranty for installation, contact your original installer. Any faults caused by poor workmanship should be covered, free of charge, by your warranty.

Birds nesting under your solar panels

"Bird and squirrels have the potential to cause significant damage to the connectors and wiring," explains Steven Cant from Which? Trusted Trader Sun Smart UK. "Birds nesting material can be combustible and present a serious fire risk".

Adding wildlife protection when your panels are installed will be "significantly cheaper than retrofitting" he adds. 

Ben Robinson, director of Exeo Energy, agrees: "installing later will be a lot more expensive to do properly with scaffolding, materials and labour".

He advises getting a professional to do the work, unless you can do it extremely carefully and safely yourself. During installation, Mr Robinson explains that it's important that:

• panels should not be drilled
• fixings should not be screwed into the frame (this will compromise the panel's warranty)
• lifting and clearing nests should be done carefully to avoid stretching tight cables or compromising connectors.

And he cautions that "most bird or pest protection will not deter a determined squirrel or jackdaw - and so should really be called pigeon protection only".

If you haven't installed solar panels yet, 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 into.

Dirty solar panels

Dirt might be caused by :

• bird droppings
• traffic pollution if you live in an urban area
• a build-up of salt if you live near the coast. 

A heavy rain storm should usually be enough to wash off most dirt. Unless the build-up is very thick or a significant amount accumulates 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.

Nathan Goldsworthy, from Which? Trusted Trader Gone Solar, suggests that you get a window cleaner to clean your panels, using only water. 

Ben Robinson, director of Exeo Energy, advises using an experienced solar panel cleaner and only cleaning them yourself if you're very careful. "Snagging of cables and smashing of panels is possible with careless cleaners. If the customer is very cautious and it is safe to do so, this could be done by them," he said.

Solar panels producing less electricity 

A drop in electricity generation is most likely caused by:

• weather conditions
• dirt building up
• a change in the environment such as shading from trees or new structures.

Misty mornings will impact the generation of east-facing panels, in particular. Thick cloud will mean that your panels produce less electricity than on bright sunny days. 

Some years are sunnier than others and this has an impact on how much electricity your panels will generate.

Less-than-perfect weather conditions are a fact of solar pv life and there’s nothing you can do about it. 

Solar panels also degrade gradually over time. So, after a decade of ownership, your panels might produce slightly less power than they did when new. You can find the expected degradation of your panels on their datasheet (search online for it using their make and model: find this on your MCS certificate).

If you suspect there might be something else behind a drop in electrical production, look at your panels and their surroundings closely to check for shade that might not have been present when your panels were installed. Also check whether there's any visible damage to your system.

If you're concerned about dirt building up, check above for how to solve this. 

A drop in generation could also be caused by a faulty DC string, suggests Richard Ellis from Which? Trusted Trader Elltec Energy Services.

Solar panels not working

If your panels aren't producing any electricity when you'd expect them to, it's most likely a fault with the inverter or problem with the wiring. 

Occasionally the generation meter might fail. If this happens, you’d see no recorded generation, even though the system is working. 

Or it might be "something as simple as the communication has been lost with the wifi, perhaps because a router has changed and the new IP address isn't recognised," suggests Ben Robinson, director of Exeo Energy.

The longer you go without your panels producing electricity, the less renewable power you'll use and the more you'll buy from the grid. Plus you'll lose out on any feed-in tariff or Smart Export Guarantee payments.

First check the solar pv breaker in your consumer unit. 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. 

Also check your inverter for any fault codes or error messages.

Broken solar PV generation meter

Check the real-time and cumulative generation on your inverter (most have these options) to make sure that the solar panels are still generating electricity. 

If the system is generating at the inverter this implies a failed generation meter.

If the fault is only with the generation meter, the panels should still be generating and feeding electricity to your property. 

But if you're claiming the feed-in tariff and don't have a smart meter, you won't be able to take meter readings (required to calculate your payments).

Contact your solar panel installer or a solar panel maintenance professional.

If your generation meter is replaced, make sure you get a letter from the installer stating what they have done and that they changed the meter because it was faulty. The paperwork should also state the model and serial numbers of the old and new meters. You'll need this to explain to your feed-in tariff supplier why your meter readings have been unusual.

Find a reputable solar panel installer using Which? Trusted Traders.

Cracked or broken solar panels

This rarely happens after installation. If you suspect that a solar panel has cracked it would most likely have been caused by impact. 

Solar panels from MCS-registered brands are made with tempered glass so will shatter rather than crack, like a car windscreen.

The cracked panel may still be generating electricity but Ben Robinson, director of Exeo Energy. advises getting it replaced as soon as possible: "This will eventually result in issues, normally as soon as moisture enters the panel".

See if you can get a replacement panel under warranty. If so, Mr Robinson advises that:

• The cost of labour for replacing the panel and any scaffolding may not be covered
• The replacement panel may look different as the technology continuously evolves
• Some manufacturers require independent testing to prove that the panel isn't performing. There are few test centres and they can be costly.

You should get a professional to replace the panel.

Isolator problems with solar panels

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
• moisture 
• sometimes burnt-out terminals owing to poor workmanship.

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.

If you suspect an isolator problem, follow the shut-down procedure that should have been left with you by your installer. If you don’t have one, turn off the PV breaker switch at the consumer unit.

You should get this issue investigated urgently by a qualified electrician or solar panel installed, advises Steven Cant from Which? Trusted Trader Sun Smart UK. They will probably use the fault codes on your inverter to do this.

If you're still choosing your solar panels, use our buying advice for solar PV guide to find the right system for your home.

* Online survey of 2,039 solar panel owners on our Which? Connect panel in April 2024.