How do I know if my solar panels are working? Four checks, and what none of them tell you

How do I know if my solar panels are working? There are four checks, and you can do the first three today with nothing but daylight. Look at the inverter’s own display or LEDs; open the brand app or portal; read your generation meter or smart meter fifteen minutes apart around midday; and, as a last resort, test a single panel with a multimeter. All four will tell you whether your system is producing right now. None of them tells you what happened in the three weeks you were not looking, and that is where almost all the lost money is.

Check one: is my solar inverter working? The display and the LEDs

The inverter is the only device in the chain that knows the truth. It sits in the garage, the loft or the airing cupboard, and it shows its state without needing Wi-Fi, a phone or an account.

Go and look at it on a bright day, ideally between 11am and 3pm.

SolarEdge. (What SolarEdge monitoring shows.) The official LED table is short: green ON means the system is producing; green blinking means AC is connected but the system is not producing; green flickering is night mode; blue ON means the inverter is talking to the monitoring platform; red ON is a system error. The combination that catches people out most is green on with blue off: producing perfectly, telling nobody. On older LCD units, S_OK on the status screen means the connection to the SolarEdge monitoring portal is working; its absence says nothing about production. Codes are written as hex digits with a literal x separating them, such as 18xB5 or 18x3. 18x3 is Night Mode, a normal status rather than a fault. The codes themselves are decoded in the SolarEdge error-code guide.

Enphase. (What Enphase monitoring shows.) The IQ Gateway (formerly the Envoy) has four separate LEDs, not one. The network LED is solid green when the gateway reaches the Enphase cloud, flashing green while it is connecting, amber or red when it has a local network but no internet, and off when there is no network at all. The power-production LED is green when all communicating microinverters are producing and amber or red when at least one is not. The device-communications LED is solid amber or red when at least one device is not communicating. All four flashing red together means the gateway is booting, which takes about three minutes. Which of them to read when panels stop reporting is set out in Enphase microinverter not reporting.

Growatt. The inverter’s own screen carries the fault codes and the day’s kWh; Growatt sets out the owner-side monitoring paths (ShinePhone, ShineServer, ShineLanBox) in its official monitoring FAQ, and the owner-side view is set out on the Growatt monitoring page. The datalogger’s LEDs are a separate story with a counter-intuitive colour scheme, and they are covered in the Growatt error codes guide. The stick’s own colour table is in Growatt datalogger red light.

What this check cannot tell you. Whether the total is right. A string inverter reports one number for the whole array, so a dead panel, a shaded string or a failing optimiser can be sitting inside a display that looks entirely normal. It also cannot tell you about yesterday: most displays show today’s kWh and a lifetime total, and nothing in between.

Check two: the brand app or portal — where “offline” is not “not producing”

mySolarEdge, the Enphase App and Growatt’s ShinePhone all give you a production graph for the day, and the useful thing about a graph is its shape. A healthy day is a smooth arc, dented by cloud. A day that stops dead at 11:20 and never restarts is a fault. A day that never rises above a fraction of your usual peak is a partial fault.

The app also tells you the health state. Enphase uses exactly three: Normal, Warning and Error. If the panels render black on the ARRAY screen, they are not sending data, which, in Enphase’s own words, “does not always mean your system has stopped producing power”. Enphase asks you to allow up to 24–48 hours for a status to update before treating it as real, and gives the same 24–48 hour window for watching a low-production condition.

Two practical traps, both extremely common:

• The account may not be yours. Plenty of systems are commissioned with the installer’s email address, and the owner is never handed the log-in. A poster who had just bought a house with panels wrote on the MoneySavingExpert forum in 2025 that, on signing up for monitoring, “they say everywhere that my installer has to do this for me, but I have no information on the installer” (thread).
• “My solar panels are offline” is not the same as “my solar panels are not producing”. If an Enphase gateway loses its internet connection, every microinverter can show as not reporting while production carries on regardless. Sorting that out is the job of the offline-or-not-producing triage guide.

I’m new to this - bought a house with panels recently … Recently I noticed that the readings don’t change and the red light is static.

What this check cannot tell you. Whether the app is telling you the truth today, and whether anyone would tell you if it stopped. The apps answer only when you open them. On SolarEdge, the alert rules live in the installer’s account, and an e-mail reaches you only if the installer has given you permission, site by site. Its no-communication alert fires only after at least three hours of silence, and by default in a daily digest.

Check three: how to check if solar panels are working from the meter, at midday

This is the check that depends on nobody’s cloud, and it is one of the ways owners on the forums catch a fault.

1. Pick a bright moment, 11am to 3pm, with sun on the panels.
2. If you have a generation meter, write down the reading, wait fifteen minutes, then read it again. It should have moved. Feed-in Tariff payments are based on submitted generation-meter readings, so FiT-registered systems were metered for generation, usually near the consumer unit or up in the loft. Many of these meters also have an LED that pulses only while generation is happening.
3. If you have no generation meter, use the export side instead: the in-home display, your supplier’s app, or the export figure on your account. A household exporting at midday is a household producing, and if you are asking why your solar panels are not exporting, this is where the answer starts.
4. If neither is available, switch on a 2–3 kW load such as a kettle or an immersion heater and watch whether your import figure barely moves. Crude, but 3 kW of generation is hard to hide.
5. A P1 dongle (a HomeWizard P1 meter or similar) plugs into the P1 port of a Dutch, Belgian or comparable smart meter and shows import and export live, second by second, on your own network. P1 is a Dutch and Belgian meter interface: UK SMETS meters have no such port, so this option is only open to you if your meter has one.

The meter is also what your money is paid on. Ofgem states that Feed-in Tariff payments are based on meter readings that generators submit, and Octopus states plainly that it “can’t make FiT payments based on estimated or inverter readings”. Under the Smart Export Guarantee you are paid per metered exported kWh. A system producing nothing exports nothing, and the payment line simply thins out without an alarm going off anywhere.

What this check cannot tell you. How much you should have produced. The meter proves the system is alive; it has no opinion about whether alive means healthy. And it is still a single moment: a meter that moves on Sunday says nothing about Wednesday. The method for putting a number on what should have come out is in check your solar production against the weather.

Check four: how do you test a solar panel to see if it is working?

With a multimeter, and this is last for a reason.

Done safely, with the string isolated at the DC switch and one panel disconnected, a multimeter across a single module gives you its open-circuit voltage (Voc), which you compare against the figure on the label on the back of the panel. A dead module reads near zero.

What this check cannot tell you. Almost everything you wanted to know. Voc proves a panel can generate a voltage; it does not prove it delivers current under load, which is the failure mode in most degraded modules. It tests one panel at a time, so on a roof of 14 panels it is 14 separate tests. And it tells you nothing about the inverter, the optimisers, the isolation resistance or the export path. Which? reported inverter problems affecting 15% of owners in an April 2024 survey of more than 2,000 members, and no multimeter reading on a panel will find one.

This, incidentally, is most of what a paid solar panel health check consists of: the four checks above, done by somebody else, on one afternoon.

How do I know if all my solar panels are working?

Worth asking separately, because the four checks above answer “is the system alive” and this one asks “is any part of it dead”. With a plain string inverter, you cannot tell: one number comes out for the whole array.

Per-panel hardware changes that. SolarEdge optimisers and Enphase microinverters both report module by module, and the difference shows up in what owners catch:

Over Christmas I noticed a panel underperforming. It was maxing out at 36w output!

And, in the same thread, the reason nobody catches it without that data:

I’d certainly not notice a 10% reduction, however 40%-60% would stand out like a sore thumb

Even with per-panel hardware, the brands do not chase this for you. Enphase’s documented thresholds: one microinverter silent for 12 hours during daylight produces a Warning in the app and no push notification at all; a notification requires at least 10% of microinverters silent for five consecutive days, and even then only “via text, email, or push notification, depending on their selected preferences”. On an 11-panel roof, one dead panel is 9%, which is below the bar, permanently. Enphase explains the logic in its own documentation:

Alert emails… are batched so they can be addressed with a single service call… A single panel that is not producing has minimal impact on the production of the array in total. By batching service calls, impacts to installer workday schedules are minimized.

That is a defensible engineering position, and it puts the installer’s van ahead of your kWh.

What none of the four checks tell you

All four are point-in-time. They describe a minute on a day you happened to care. The failures that cost real money are the ones that begin on a day you did not, and in dozens of these stories what causes solar panels to stop working matters far less than how long it took anyone to notice.

Gutted to get back from holiday and find that the inverter stopped with an error on the day we left. 2 weeeks of prime August generation lost :( All it took was a turn off for 10 mins, then back on to resolve it but as we were away we lost out.

The other pattern is slower and far more common: nothing looks broken, so the shortfall gets put down to the weather until a bill turns up.

I received a electricity bill from half a year and I was rather shocked by the amount I had to pay. This bill made me wonder whether my solar panels actually work properly.

The bill is the slowest detector in the house. It arrives monthly at best, quarterly or half-yearly for many people, and it mixes production, consumption, weather and tariff changes into one number you cannot take apart.

Is there an app to monitor my solar panels? What each one does

Every option above the last one is a better display, and a better display still needs you to open it. Solmiro watches inverter production only (not batteries, not consumption, not tariffs) for SolarEdge, Enphase and Growatt, and connecting is free.