A solar panel health check you can do yourself has six steps and takes about a quarter of an hour: confirm it is producing right now, hold last full month against what the weather should have given you, find out whose inbox the alerts go to, read any code or LED, note the system’s age and what is still covered, and then look at what none of that catches. The first five you can finish today with the app you already have and one free tool from the European Commission. The sixth covers the losses that are hardest to notice: the ones that leave the inverter running, error-free and quietly short.
Work through the steps in order. Each one rules out a class of fault, and the cheap ones come first.
Step 1: is it producing right now?
Go out to the inverter, or open the manufacturer’s app, on a bright day between roughly 11am and 3pm. You want two things: a live power figure in watts that is not zero, and a curve for today that has been climbing since morning. A dark display, a portal saying the site is not communicating, or a graph flat at zero through the middle of a sunny day are all worth acting on straight away. Start with the inverter offline triage, which separates “the monitoring is broken” from “the system is down”.
Note down what you see, including the date and the time. Even if you never run this check again, one dated reading of a working system is worth having, because it tells you later when the system was last definitely alive.
This step only tells you about this minute. It says nothing about the three weeks you were not looking, and nothing at all about whether the number in front of you is the number it should be.
Step 2: does last month’s output match the weather?
Your app knows how many kWh you produced; it does not know what the sky was doing, so it cannot tell you whether that number was any good. You supply the missing half.
PVGIS, the European Commission’s free solar calculator, estimates what a system of your size, tilt and orientation should produce where you live. The short version of the walk-through, using the tool’s own labels:
- Set your location: click on the map, type an address, or enter latitude and longitude.
- On the GRID CONNECTED tab, choose the Solar radiation database and the PV technology offered for your location.
- Enter Installed peak PV power [kWp]: the nameplate figure on your paperwork, which the array makes in test conditions (1000 W of sunlight per square metre, at 25°C), not something your roof ever reaches in ordinary light.
- Leave System loss [%] at its default of 14% unless you know better. It is a default, not a measurement of your installation.
- Enter Slope [°], the angle of the panels from horizontal, and Azimuth [°]. Get the azimuth sign the right way round, because it is the easiest thing to reverse: −90° is east, 0° is south and 90° is west.
- Run the calculation and read the monthly graph in the results.
Then compare: last month’s kWh from your app against the PVGIS figure for that month. A single day proves nothing, because a day is dominated by that day’s cloud. A month that lands well below the estimate in ordinary weather is worth looking into. The full method, including why comparing with last year misleads you, is in the guide on checking solar production against the weather.
The reference has two limits of its own. PVGIS gives a long-run average, not a report on the weather your roof actually had, so a genuinely dull month will undershoot it with nothing wrong. And it is built from satellite data, so treat it as a yardstick for your roof rather than a measurement of it.
Step 3: who gets the alerts?
It is easy to assume that if the system stopped, somebody would tell you. On each brand that depends on settings someone else may have made, so check them.
SolarEdge. Alert rules sit in the installer’s account, and your e-mail only receives alerts if the installer has ticked “Expose to alerts notifications” for you. Even then, a silent inverter is flagged after three hours at the earliest, and by default in a daily digest. Ask your installer which rules are switched on for your site.
Enphase. In the app, open Menu → Account → My Notifications and choose Email, Text or Push. Texts need a registered mobile number. The low-production alert only fires if a Production Threshold has been set on your site, so ask whether one has.
Growatt. The alert tick-boxes are in the ShineServer web portal, and they go to the mailbox the plant was registered with, often the installer’s. Log in, open the plant settings and check both the address and the boxes.
Open your own account settings and find out which address is on file. The guide on who gets your solar alerts sets out the settings to check, brand by brand.
Step 4: any error code or red light?
Write down whatever the display or app shows, exactly as it appears, before you reboot anything, because a reboot can clear the evidence along with the fault.
- SolarEdge: the status string and the LED colours are the starting point. Codes and what they mean are in the SolarEdge error code guide.
- Growatt:
Error 203andError 117are the codes covered in the Growatt 203 and 117 guide, along with the damp-morning pattern behind them. A red LED on a Growatt datalogger (the small comms unit that sends your data to the portal) is a different device from the inverter, and its LED colours have their own meanings: the datalogger red light guide works through them. - Enphase: a “Microinverters Not Reporting” message can point at the comms path rather than at dead panels. The Enphase not reporting guide works through which of the two you have.
No code is not the same as no fault. Step 6 is entirely about the faults that never produce one.
Step 5: how old is the kit, and what is still under warranty?
Find the commissioning date and the paperwork. Two things follow from them.
The first is the age question. Which?’s member survey of April 2024 (n > 2,000) found 15% of owners had experienced inverter problems, the most common technical issue reported. And the UK’s installed base skews old: 841,825 UK installations were in place by December 2015 (DESNZ), so a large cohort is now well past ten years. On lifespan, the published figures come from cost sites, not manufacturers: The Eco Experts (30 July 2024) says string inverters cost £500 to £1,000 and usually last around 10 years; GreenMatch (19 February 2025) gives £500 to £1,500 for a replacement and 5 to 10 years for most inverters, 10 on average. Those are estimates, not warranty terms.
The second is the claim window. Your own warranty document is what tells you what is covered and for how long, so read that rather than a generic figure. The timing matters too: a fault you have not noticed is a fault you have not claimed, and the window keeps running whether or not anyone is watching. If the company that installed the system has since gone under, the installer gone bust guide covers what happens to the monitoring account and to the paperwork.
Export income is the quiet part of the same question. Under the Smart Export Guarantee, launched on 1 January 2020, the supplier you choose pays you for each kWh you export, at a rate and on terms it sets. So a system producing less earns less, in proportion. Ireland’s Clean Export Guarantee works the same way, per metered kWh exported, so fewer kWh out of the meter means less on the export line of the bill, and nothing tells you it has happened.
Step 6: what a one-day check cannot see — underperformance with no fault showing
Everything above is a point-in-time check on a system that is either alive or dead. The loss that is hardest to catch is neither. It is the system that stays online, reports no fault, and produces less than it should for months on end.
A whole string (one series-wired run of panels feeding the inverter) can go dead with the inverter reporting nothing at all:
Since installation the generation figures have been slightly lower than before but I put this down to cloudier weather and deterioration of the solar panels. However when I checked the inverter I noticed that whilst string 2 was working fine, string 1 had the correct voltage (360v) … but the ampage was zero and hence not generating any output. The inverter appeared to be working fine and had no error messages.
In the first sentence, the owner explained the shortfall away as weather. That is an easy explanation to reach for, and it is why a slow loss can run for a very long time before anyone tests it against a number.
The brand alerts will not catch it either. Enphase’s low-production alert only fires if a Production Threshold has been set, and per-panel alerts are an Installer Portal feature. Growatt’s alert boxes go to whoever registered the plant. And SolarEdge’s alert rules are the installer’s to switch on, as step 3 showed.
The discovery then falls to whatever number reaches you next, which is often a bill:
I didn’t notice anything amiss until September, 2021 when I got an unexpected power bill. When I looked at the Solar Edge monitoring data, power production starts to noticeably drop first in March, 2021 and I thought that the problem started around then.
The decline ran for six months before the owner noticed it, with a monitoring platform open the whole time.
What to do with the result
If steps 1 to 5 all came back clean, you have established that the system is alive today, that last month landed roughly where it should have, that you know whose inbox the alerts go to, and that you know how old the equipment is. That is useful, and it holds for about a day. Solmiro repeats the weather check every day: it works out what the weather over your roof allowed, and it e-mails you when production falls well short of that or stops. Connecting is free.
If the monthly comparison came back low, take it to the producing less than expected guide, which orders the partial-loss causes by likelihood: one string or MPPT down, a dead optimiser or microinverter, grid over-voltage curtailment, shading that has grown, soiling, and heat derating.
If step 3 turned up an address you do not control, sort that out regardless of what the rest of the check found. The alert settings to change, brand by brand, are in the alerts guide, and the how do I know if my solar panels are working guide covers the same ground for an owner with no portal login at all, which is common after buying a house with panels already on the roof.
What the monthly check looks like on a real roof
On a 6.09 kWp Enphase roof in Almere that Solmiro checks every day, August 2026 came to 214 kWh against the 221 kWh the weather allowed on 10 comparable days (97 %), and September came to 468 kWh against 467 kWh on 28 comparable days (100 %). Single days swing much further, from 66 % on 18 September to 217 % on 2 September, and the roof was back above 100 % on the following comparable days. So Solmiro never alerts on a single day: a shortfall only counts when it lasts over several comparable days.
Questions owners ask
How do I check if my solar panels are working?
Look at the inverter or its app around midday on a bright day: it should show watts flowing now and a curve for today that has been climbing since morning. That answers the question for this minute only. To know whether the panels are working properly rather than merely working, you need the second half of the check — last full month's kWh held against a PVGIS estimate for your own roof.
How do I know if all my solar panels are working?
A string inverter reports one total for the array, so a single dead panel, or a whole dead string, is not broken out separately in that figure. On a system with optimisers or microinverters the portal shows a per-panel layout, and a panel reading zero while its neighbours produce is the thing to look for, though on Enphase per-panel alerts are an Installer Portal feature. Otherwise the shortfall shows up as a monthly total sitting below what the weather should have delivered.
How old does an inverter have to be before I worry?
Two UK cost sites put it at about ten years. The Eco Experts (30 July 2024) says string inverters “usually last around 10 years”; GreenMatch (19 February 2025) gives 5 to 10 years for most inverters, 10 on average, and up to 25 years for microinverters. Those are estimates, not manufacturer terms: your own warranty document decides what you can claim.
Is a solar panel health check worth paying for?
PVGIS, the European Commission's solar calculator, is free, and the rest of the check uses the app you already have, in about a quarter of an hour. Paying for help is the normal step after that: Which?'s April 2024 member survey (n > 2,000) records that 82% of inverter replacements were done by professionals. What the desk check gives you first is a reason to make the call.
What does a 15-minute check not catch?
A partial loss that leaves the inverter running and error-free: one dead string, one dead optimiser, shading that has grown, or an inverter derating on high grid voltage. Nothing shows a fault, the system stays online, and the monthly total is simply lower. On Enphase, the low-production alert only fires against a Production Threshold, and only if one has been set.