Quick answer
Under-production comes from soiled panels, shading, wrong tilt or orientation, an undersized or mismatched MPPT, or a failed string. Your monitoring portal is the fastest diagnostic tool you have — it shows which strings underperform and at what time of day, and that pattern usually identifies the cause before anyone climbs onto the roof. Highveld dust alone can cost a substantial percentage.
Common causes
- Dust and soiling, which builds up quickly through a dry Highveld winter
- Shading from trees, aerials, chimneys or a neighbour's structure
- Wrong tilt or orientation limiting the yield the array can ever achieve
- MPPT undersized or strings badly matched to the inverter
- Failed string, blown fuse or a faulty optimiser
- Bird droppings and nesting under the array, common and often overlooked
What you can do now
- 1Check the monitoring app daily and note which strings underperform and when
- 2Clean the panels roughly every six months, more often after a dry winter
- 3Photograph shadows across the array at different times of day
- 4Compare current output against the same month last year rather than against the brochure
- 5Check under the array for bird nesting
When to call a professional
Persistent shortfalls need an installer site visit with the monitoring data in hand. Bring the string-level figures — they turn a speculative roof inspection into a targeted one. If shading is structural rather than seasonal, the fix may be optimisers or a re-string rather than more panels, and that is a much cheaper conversation to have early.
Typical cost in Johannesburg
Service + clean R950 · Optimiser fit R1,400 each
Indicative ranges only. We provide written, itemised quotes before any work.
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