Path-Q Solar

How should inverter capacity be chosen when panels may produce their highest output at different times?

Answer

Choose inverter capacity from the combined time profile of the array, not by simply adding every panel's nameplate rating. Panels with different orientations or shading may spread production across the day, allowing a design with a lower inverter-to-array ratio, provided expected clipping, voltage, current, and equipment limits are acceptable.

Key points

  • Nameplate panel output is not normally sustained simultaneously under real operating conditions.
  • Different orientations can reduce coincident peaks and may reduce clipping.
  • The design should model annual production and peak conditions for each roof group.

What it depends on

  • Panel orientation, tilt, and shading
  • Local solar conditions and temperature
  • Array-to-inverter sizing ratio
  • Inverter input, voltage, current, and operating limits

Risks and trade-offs

  • An undersized inverter can clip production during high-output periods.
  • An oversized inverter may cost more without materially increasing annual energy.

Information you may need

  • Array layout and module ratings
  • Hourly production model by roof section
  • Inverter datasheet and expected clipping estimate

Your next step

What to do next

Ask the designer to show expected annual clipping and peak output for the proposed inverter size and at least one alternative.

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SQ01410