East-West Layout

Key Takeaways

• East-west layout = alternating east + west facing modules.
• Flatter daily profile than south-facing.
• Common in carports and NEM 3.0 residential.
• Requires separate MPPTs per orientation.
• Yields ~5–10% less than ideal south-facing but more space efficient.

Why East-West Layouts Get Chosen

The decision to split an array into east-facing and west-facing rows instead of orienting everything south is rarely about maximizing total kWh — it’s about reshaping when that kWh shows up. A south-facing array concentrates output around solar noon; an east-west array spreads it into a broader, flatter shoulder-to-shoulder curve. That flatter profile is worth more than raw output in three recurring scenarios: carports, where the structure’s orientation is fixed by parking-row geometry rather than by azimuth optimization; low-tilt commercial roofs, where rows angled back-to-back let more modules fit per unit of roof area for a given tilt angle; and NEM 3.0 residential systems, where morning and evening production lines up with the export windows that actually pay.

String and MPPT Design

Because east-facing and west-facing rows peak at different times of day, they cannot be wired onto a single MPPT without giving something up — the tracker will settle on a compromise voltage point that under-harvests both strings, producing the 4–8% combined-MPPT loss noted above. The standard fix is to keep east and west sub-arrays on separate MPPT inputs so each half of the array is tracked independently. On systems with tighter mismatch — partial shading between rows, or module-to-module variation within a single orientation — a module-level DC optimizer can recover more of that loss than a string-level MPPT split alone, at the cost of added hardware and a per-module point of failure.

Related Reading

East-west layouts only pay off if the flatter profile is actually modeled and priced correctly before construction, which is why the trade-off shows up as a line item in yield reports rather than a rule of thumb applied by eye. Our guide to PV yield simulation software covers how tools like PVsyst quantify the east-west yield penalty against a south-facing baseline for a specific roof or carport geometry, and our explainer on P50/P90/P99 in solar yield reports walks through how that modeled output translates into the confidence bands a lender underwrites against. When the layout decision is driven by a carport or low-tilt commercial roof rather than a standard pitched residential roof, it’s worth reviewing it alongside our solar ground mount design service, and where east-west rows are being laid out and shading-checked in 3D before the structural drawings are finalized, that’s exactly the modeling step our Solar 3D Pre-Design service handles.