Comparisons
String inverter or microinverters on a shaded roof
Choose a string inverter with optimisers on the shaded panels: it captures most of the benefit at a fraction of the cost of full microinverters. Go to microinverters only where shade is severe and scattered across the array, or where panels face genuinely different directions.
Last reviewed
Why shade costs more than its area suggests
Panels in a string behave somewhat like links in a chain — a shaded panel drags the string's output below what the unshaded panels could produce. Bypass diodes limit the damage but do not remove it. This is why a boundary wall shading one corner for two hours can cost far more than a proportional share of the day's generation.
What optimisers do
A power optimiser sits behind an individual panel and lets it produce independently of the rest of the string. Fit them only on the panels that are actually shaded and you get most of the benefit of module-level electronics for a small fraction of the cost of converting the whole array. For the typical Pakistani roof with one shaded corner, this is the right answer.
When microinverters genuinely win
Shade that moves across many panels through the day, an array split across roof faces pointing different directions, or a roof so broken up that no two panels share conditions. In those cases per-panel conversion is not an upgrade, it is the only arrangement that works — and the extra cost buys energy you would otherwise never collect.
The cheaper fix people overlook
Before spending on electronics, check whether the shade can be removed or the array moved. A water tank relocated, a parapet lowered, or the array shifted two metres will often outperform any inverter topology and cost less than the optimisers would. Survey the shade across a full day before deciding it is permanent.
Do I need microinverters if my roof has shade?
How much output does shade actually cost?
More than its area, and it depends on the string layout. A single panel shaded for part of the afternoon can pull its whole string down for that period. This is exactly why a shading survey belongs in the quotation stage — shade is invisible on a satellite view and very visible on a generation log six months later.
Are microinverters more reliable?
They distribute the risk: one failure takes out one panel rather than the array. Against that, you have many more units on the roof, each in a hot position, and replacing one means going back up. Neither arrangement is clearly more reliable in practice; they fail differently.
Can I add optimisers to an existing array?
Usually yes, if the inverter supports them, and it is a common fix when a system underperforms because shade was not surveyed properly at installation. It is cheaper than replacing the inverter and far cheaper than moving the array. The first step is measuring which panels are actually losing output, not guessing.
Rather have it done?
When a solar system stops producing, the fault is usually the inverter, a string connector or a tripped protection device rather than the panels themselves. Diagnosis in Islamabad or Rawalpindi starts at PKR 5,000, taken off the bill if you go ahead with the repair.
Solar inverter and panel repair in Islamabad — prices and scope