Path-Q Solar

How should an inverter be selected when the array has unequal numbers of panels on different roof planes?

Answer

Prefer an inverter architecture that gives each materially different roof plane its own MPPT, or use separate inverters where necessary. Each MPPT should normally serve panels with similar orientation, tilt, shading, and string voltage; unequal panel counts are acceptable only when each input remains within its electrical limits.

Key points

  • Separate MPPTs prevent one roof plane from forcing a shared operating voltage on another.
  • A shorter string may have insufficient voltage even if its wattage is acceptable.
  • Some inverters allow multiple strings on one MPPT, but those strings generally need compatible voltage and similar operating conditions.
  • Module-level electronics can provide more layout flexibility but add devices and cost.

What it depends on

  • Panel count and electrical ratings on each roof plane
  • Roof orientation, tilt, and shading
  • Number and operating range of inverter MPPTs
  • String voltage and current limits

Risks and trade-offs

  • Using one MPPT for dissimilar planes can cause mismatch losses.
  • Choosing an inverter with too few inputs may require awkward stringing or additional equipment.
  • More MPPTs or module-level electronics can improve flexibility but may increase cost and maintenance points.

Information you may need

  • Panel layout by roof plane
  • Panel voltage and current ratings
  • Inverter MPPT count and input limits
  • Shading analysis and expected production by plane

Your next step

What to do next

Compare a single inverter with sufficient independent MPPTs against separate inverters or module-level electronics using the actual roof-plane string designs.

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SQ01878