POA Irradiance (Plane of Array)

POA Components

POA_total = POA_direct + POA_diffuse + POA_reflected

POA_direct = DNI × cos(incidence_angle)
POA_diffuse = DHI × transposition_factor_diffuse
POA_reflected = GHI × ρ_ground × (1 − cos(tilt)) / 2

Where ρ_ground is the ground albedo, the fraction of incident light the ground surface reflects back onto the module’s rear or front face.

Transposition Models

POA vs. GHI Examples

Key Takeaways

• POA = total solar radiation on tilted module surface.
• Direct + diffuse + reflected, transposed from GHI/DNI/DHI.
• Perez transposition is the bankable industry standard.
• POA = GHI × ~1.05-1.20 typically for optimal tilt.
• Bifacial designs compute POA_front and POA_rear separately.

Related Reading

POA irradiance is the direct input that transposition models feed into a plant’s expected energy yield, and it shows up throughout the yield-simulation workflows covered in Solar Simulation Software 2026: Lender-Grade Yield Picks. Because the transposition factor is sensitive to row spacing and shading, engineers building ground-mount layouts often reference our PVsyst 3D near-shading scene builder walkthrough before finalizing tilt and pitch. On tracker-based plants, backtracking changes the incidence angle used in the POA_direct term hour by hour, a process detailed in PVsyst Tracker Yield Study: Step-by-Step Methodology. Once POA-derived yield numbers are in hand, they typically flow straight into project economics, SurgePV’s solar generation financial modeling tool is built around that handoff from irradiance to revenue projection.