Data · 6 min · Updated 11 October 2026

How to read your solar production data

Short answer: Read kW as power right now and kWh as energy over time. Judge your system on monthly and yearly kWh per kWp, compared with a realistic benchmark from the EU's free PVGIS tool for your address and roof. Season and weather explain most low days. A sudden drop on clear days, a flat low peak or a recurring alarm points to a real fault.

Solar apps such as Huawei FusionSolar and FoxESS FoxCloud show a lot of numbers. This guide explains which ones matter and how to tell normal variation from a problem.

The numbers on your screen

Figure	Unit	What it tells you
Current power / PV	kW	What the panels deliver right now
Today's yield	kWh	Energy produced since the morning
Monthly and yearly yield	kWh	The figures to compare over time
Consumption / Load	kW, kWh	What your home uses. Needs an installed meter.
Grid import and export	kW, kWh	Power from and to the grid. Needs an installed meter.
Battery	% and kW	State of charge, and whether it charges or discharges
Alarms	ID and text	Faults reported by the inverter

A useful rule: kW is a snapshot, kWh is the result. Three hours at 2 kW gives 6 kWh.

If consumption or grid figures look odd while production looks fine, the meter link may be the problem. Both Huawei (2067 Faulty Power Collector) and FoxESS (Meter Lost Fault) have specific alarms for it.

Normalise to kWh per kWp

To compare your system with a benchmark, divide the yearly yield by the system size. A 6 kWp system that produced 5,400 kWh in a year has a specific yield of 900 kWh/kWp. Your system size in kWp is in the paperwork from your installer.

Find a realistic benchmark with PVGIS

PVGIS is the free solar calculator from the European Commission's Joint Research Centre. Enter your address, panel size, tilt and orientation, and it estimates monthly and yearly production. You can use it at PVGIS.

Orientation and tilt matter a lot. As an example, here is what PVGIS gives for one location (Odense, Denmark; 1 kWp crystalline silicon, 14 percent system loss, PVGIS-SARAH3 radiation data):

Setup	kWh per kWp per year (PVGIS)
South, 35 degrees	1,011
South, 10 degrees	908
East, 35 degrees	793
West, 35 degrees	791
South, vertical (90 degrees)	740

Your own numbers will differ by location, but the pattern holds: east/west and flat or vertical panels produce less per kWp than a well tilted south-facing system (north-facing in the southern hemisphere). That is not a fault.

Read the daily curve

On a clear day the production curve should look like a smooth bell, peaking around midday.

What you see	Likely cause
Smooth bell, lower than in summer	Season. Normal.
Jagged curve	Passing clouds. Normal.
Dip at the same time every day	Shading from a tree, building or chimney
Flat, low peak on a clear day	Part of the system may not be delivering
Production stops and restarts on sunny days	Possibly grid voltage faults. Check alarms.
Zero and offline	Communication problem. Production may be fine.

Compare month by month

A single grey week says little. Compare the same month year on year in the app, and compare each month with PVGIS's monthly figures. Production in winter is naturally a fraction of summer production at higher latitudes.

Typical causes of low production

Cause	Sign	What to do
Weather and season	Low across the area, matches the season	Nothing
New shading	Drop at certain times every day	Find the source
String dropped out	Low peak on clear days, smooth curve	Contact installer
Inverter fault	0 kW and an alarm in the app	Look up the alarm and call
Dirt and snow	Gradual drop or snow cover	Clean only if clearly needed
Communication	App shows 0 or offline	Check Wi-Fi. Production may be fine.
Ageing	Slow decline over many years	Normal. See below.

Ageing: panels lose a little output over time. A widely cited review by Jordan and Kurtz of the US National Renewable Energy Laboratory (2012) found a median loss of 0.5 percent per year across almost 2,000 measurements. That does not explain a sudden drop.

Dirt: a study by the German Aerospace Center (DLR) on soiling in Europe finds that losses are generally low in northern European countries, because rain cleans the panels. Drier and dustier regions see larger losses.

When to call

Production is zero on a bright day and there is an alarm.
The peak on clear days is clearly lower than at the same time last year.
The same fault keeps returning.
You can see physical damage to panels or cables. Do not touch anything.
Huawei inverter alarm codes explained
FoxESS error codes explained
Is solar monitoring worth it?

FAQ

What is the difference between kW and kWh in my solar app?

kW is power at this moment. kWh is energy over time. A system producing 3 kW for two hours produces 6 kWh. Your daily, monthly and yearly totals are in kWh.

How much should my solar system produce?

It depends on location, orientation, tilt and shading. The EU's free PVGIS tool estimates expected yield for your address and setup. As an example, PVGIS gives around 1,011 kWh per kWp per year for a south-facing system at 35 degrees near Odense, Denmark.

Do east or west facing panels produce less?

Yes, per kWp. In PVGIS, a system near Odense at 35 degrees gives around 1,011 kWh/kWp facing south and around 790 kWh/kWp facing east or west.

Can part of my system stop working without me noticing?

Yes. If part of the panels stops delivering, the inverter can still produce with the rest. It shows most clearly on a clear day, when the top of the production curve is lower than normal.