How to read panel-level data in your solar app

If your array has microinverters or optimizers, your app can show what each panel makes. Read fairly, that view points straight at the panel that needs a look.

What is panel-level data?

It is production reported panel by panel instead of for the whole system. Arrays with a small electronic unit behind each panel, either a microinverter or an optimizer, can send each panel’s figures to your monitoring app.

Arrays with a single string inverter on the wall usually cannot. They report one total, sometimes split into two or three strings. That is still useful, just coarser.

Not sure which you have? Your monitoring app will tell you. If it shows a map of your roof with a tile for every panel, you have panel-level data.

Where do you find it in the app?

Most apps call it something like the array view, layout or panel view. It shows a map of your roof with each panel shaded by how much it produced.

• Daily energy: each panel’s kilowatt-hours for one day. The most useful view.
• Live power: each panel’s watts right now. Jumpy, and easy to misread.
• Per-panel history: a graph for one panel over days or weeks.
• Lifetime totals: handy for comparing panels on the same face over years.

Our guide to reading your solar app walks through the daily, monthly and panel views step by step.

What does a healthy array look like?

Even, within each roof face. Panels on the same plane, with the same tilt and the same sky, should finish a clear day within a small margin of each other.

Between faces, expect differences. On a roof with panels on the east and west sides, the east panels lead in the morning and the west panels catch up in the afternoon. Their daily totals can differ a lot without anything being wrong.

Edges and corners often run a little lower than the middle, especially near chimneys, vents, dormers and trees. That is shade, and it repeats every day at the same hours.

How do you compare fairly?

Choose the right day and the right neighbors.

• Clear days only: a passing cloud hits panels unevenly and makes noise.
• Daily totals: a single moment’s power reading changes with every gust of haze.
• Same roof face: compare a south panel with south panels, not with the garage roof.
• Same season: compare November with last November, not with June.
• Several days: one odd day is noise; a pattern over a week is information.

Do that, and the panel that really is low stands out clearly from the ones that are simply placed differently.

Which patterns mean what?

Here are the shapes we see most often on Front Range roofs, and what they usually point to:

• One panel at zero all day: a communication drop or a unit fault. A question for your installer.
• One panel low every day: shade, a bird dropping, a crack, or a failing unit.
• A cluster low in the morning only: shade from a tree, chimney or neighbor’s roof.
• The whole bottom row lower: a dirt line along the frames, or snow lingering at the eave.
• A whole face lower after a storm: worth checking for hail damage from the ground.
• Everything drifting down slowly: a soiling film building through a dry season.

Season changes the shade picture too. In winter the sun sits low and a tree that never touched your panels in July can shade the bottom row by early afternoon. In spring that same tree leafs out and moves the shadow again.

What about gaps in the data?

Gaps are common, and most are not about the panels at all. Panel-level data travels from each unit to a small gateway in your house, then over your internet connection to the app. Any break in that chain shows up as missing or zero figures.

• The whole array blank for hours: usually the gateway or home internet, not the roof.
• Gaps after a new router: the gateway may need to be reconnected to the network.
• One panel blinking in and out: a weak signal from that unit, or a unit starting to fail.
• Figures that fill in later: many gateways store data and upload it once they reconnect.

A quick way to tell a data gap from a real outage is your utility meter. If it shows the house exporting on a sunny afternoon while the app shows nothing, the panels are working and the reporting is not. Your installer can help reconnect the gateway.

What does the bottom row tell you?

More than people expect. When rain or snowmelt runs down the glass, it carries dirt to the bottom frame and leaves it there. Over a season, that line sits right across the lowest cells.

In winter, snow also lingers longest at the lower edge of each panel, where it meets the frame or the gutter. A bottom row that recovers more slowly after every storm is often just snow and ice holding on in shadow.

Neither is a fault. Both show up neatly in panel-level data as a row that trails the rest.

When is a drop worth acting on?

When it is big and it lasts. A method published in Solar Energy by researchers at UTS, UNSW and Diagno Energy offers a useful yardstick. It flags major underperformance when output stays below 60% of expected for three non-cloudy days, and minor underperformance below 80% for seven days. It was tested on 1,089 Australian PV systems.

That method works on whole-system data from the inverter. You can borrow its logic at the panel level:

• A panel far below its neighbors for three clear days: call your installer.
• A panel a little below its neighbors for a week: take a look from the ground, then decide.
• A short dip that recovers: probably weather, shade or a passing bird.

“Expected” is the hard part for owners. On a single face, the easiest expected value is simply the panels around it.

What can you check yourself?

Quite a lot, from the ground. Walk out on a clear morning with binoculars and look at the panel the app has flagged.

• Something on it: a dropping, leaves, a cottonwood seed mat, a slab of old snow.
• Something over it: a branch that has grown into the sun path.
• Something wrong with it: a crazed white web in the glass, or a bent frame.
• Something under it: twigs or feathers poking out, a sign of nesting.

Do not climb onto the roof to check, and do not open anything electrical. If the panel looks clean and unshaded and still reads low, it is a question for your installer, who can test the unit behind it.

What does the monitoring desk do?

Reads your data so you do not have to. With your permission and read-only access to your app, our performance monitoring service checks your production against what it should be and flags a panel or string that falls behind.

When something shows up, you get a short note saying what we see, what it probably means and who should look at it. Sometimes that is us with a brush. Often it is your installer. Occasionally it is nothing, and we say so.

Output watch is from $12 a month or $129 a year. It is also part of year-round care.

What if you only have a string inverter?

You can still do a lot. Compare clear-day totals week by week, and use the 60% and 80% yardstick on the whole system. You will not see which panel is low, but you will see when something changes.

Then a visual solar inspection can do what the data cannot: look at every module, photograph it, and note anything cracked, browned, loose or nesting underneath.

Where to go from here

Open your app, find the array view, and look at a clear day from last week. If one panel stands apart from its neighbors, start with our checklist for when your production drops, or send us a screenshot for a free read. If you would like someone watching it every month, you can book output watch.