#Solar Monitoring: How to Read Output Data Correctly

Monitoring answers one question: is the array doing what it should be doing today, given the weather it actually had? Almost every misdiagnosis comes from comparing today's number against nameplate rather than against expected conditions.

Nameplate output is a laboratory figure measured at 1000 W/m2 and 25 deg C cell temperature, the standard test conditions defined by the IEC. A roof in July runs far hotter than that, and crystalline silicon loses roughly 0.3 to 0.4% of output per degree above the rating. A system producing below its sticker on a bright summer afternoon is usually behaving exactly as designed. The same system producing well below a neighbouring string on the same roof, same orientation, is not.

String comparison is the most useful diagnostic available to an owner. Two strings of similar size and orientation should track each other through the day. A persistent gap between them, especially one that appears at the same hour each day, points to shading or to a fault localised in one string rather than a system-wide problem.

Standby behaviour at night confuses more owners than any other reading. The inverter continues drawing a small amount of power to keep its monitoring and communications alive, which shows in the app as consumption without generation. It is normal, it is small, and it is not a fault.

Physical inspection still has a place. Cracked cells, delamination, discoloured backsheets and hotspots are visible problems that no dashboard reports directly, though they eventually show as a quiet decline in one string's output.

These articles cover what the inverter readouts mean, the seven physical signs worth checking, and how to separate a genuine underperformance from ordinary temperature and weather effects.