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Can an east-west solar system beat a south-facing one?

Short answer

Not on total energy per panel: an east-west array makes about 80% of what the same panels would make facing south. It can win on value, because output starts earlier and runs later, matching morning and evening use, and because more panels usually fit across two roof faces, often without inverter clipping.

Last checked 24 September 2026 · 1 source

In more detail

  • PVGIS London 30 deg: east 830, west 805, average ~818 kWh/kWp vs south 1,014 (~81%).
  • Summer: east ramps from early morning, west generates into the evening (e.g. ~8pm in August).
  • Because the two faces peak at different times, an east-west array can be DC-oversized onto a smaller inverter with little clipping.
  • Where a south roof is small, using both east and west faces can give more total kWh than the south roof alone.

The facts, dated

  1. 01
    PVGIS London: east-west average ~81% of south per kWp — ~81 %

    market_data · England · checked 24 September 2026 · PVGIS (EU Joint Research Centre)

What we saw in the field

[QA review 2026-09-24] I-3 CONTRADICTS per kWp; plausible only for total roof output with more panels. | Earlier notes: Installer claim 'east-west can outperform south overall' CONTRADICTS PVGIS on kWh per kWp; it holds only if 'overall' means more total panels, more self-consumption or less clipping. Customer 1's timing (east from ~8am, west to ~8pm in August) agrees with the physics.

Sources

Last checked: 24 September 2026