A drop in generation has a manageable set of possible causes, and they can be narrowed down considerably before anyone climbs onto the roof. The most useful first question is whether the fall was sudden or gradual, because that alone rules out about half the possibilities.
What maintenance actually involves
Gradual decline over weeks points to soiling or progressive shading. A sudden drop on a specific date points to a fault — a tripped isolator, a failed string, an inverter problem. A seasonal decline that recovers is usually just the monsoon. Establishing which of these three patterns you are seeing is the whole of the initial diagnosis, and your monitoring history is what tells you.
| Pattern | Likely cause | First check |
|---|---|---|
| Gradual decline over weeks | Soiling accumulation | Inspect glass, clean, compare output |
| Sudden drop, one clear date | Tripped isolator or protection device | Check DC and AC isolators, inverter display |
| Drop at the same time daily | New shading on part of the array | Observe array at that hour |
| Output halved | One string offline | Compare string figures in monitoring |
| Seasonal, recovers later | Monsoon cloud cover | Compare against last year, same month |
| Zero output | Inverter fault or supply issue | Check inverter status, then call technician |
A first-pass diagnostic. Anything requiring the DC side to be opened, or any work beyond visual inspection and isolator position, should be handled by a qualified technician.
The engineering view
Two causes are commonly misread. The first is partial shading: because modules in a series string perform close to the weakest, a small new shadow — a water tank moved, a parapet extended, an antenna installed — can cost far more output than its size suggests. The second is a single failed string on a multi-string system, which halves or thirds output without any error being displayed prominently, and is easy to miss unless monitoring reports at string level.
Local operating conditions
Monsoon-season drops in Karnataka are large enough to alarm owners who are comparing against pre-monsoon months. Comparing the same month year on year is the reliable check. Construction near Bengaluru rooftops is also a frequent cause of both accelerated soiling and genuinely new shading, sometimes appearing within months of commissioning.
Common mistakes to avoid
Diagnosis usually goes wrong before anyone reaches the roof:
- Comparing output against the previous month rather than the same month last year
- Assuming a fault when soiling or monsoon explains it
- Overlooking new shading from recent construction or growth
- Missing a dead string because only total output is being monitored
- Opening DC connections without the training to do so safely
What we recommend
Start with your monitoring history and establish whether the drop was sudden, gradual, or seasonal. Clean the panels and check isolator positions before calling anyone. If output is still short after that, string-level data is what a technician will want, so have it ready.
Common questions
- My output halved overnight. What happened?
- A halving usually means one string has gone offline, often through a tripped protection device or a connection fault. It needs a technician, but string-level monitoring data will speed up the visit considerably.
- Is lower monsoon output a fault?
- Almost never. Karnataka generation drops to roughly two-thirds of the annual average during the monsoon months and recovers afterwards.
- Can a single panel cause a big drop?
- In a series string, yes. Modules perform close to the weakest in the string, so one shaded or failed module affects far more than its own share.
- How do I know if cleaning will help?
- Note your output, clean, and compare over the following days under similar weather. If cleaning recovers the gap, soiling was the cause.
- Should I check anything myself?
- Visual inspection and isolator positions are reasonable. Anything past that, particularly on the DC side, should be left to a qualified technician.
Talk to our engineering team for a solar assessment.
We will review your consumption, roof, and site constraints before recommending any capacity.