Plane-of-array irradiance is the sunlight falling on the surface of the PV modules at their actual tilt and orientation. It is reported in W/m2. It is made up of three components: direct beam, diffuse sky light and ground-reflected light (albedo). If a pyranometer is mounted at the same angle as the modules, it measures POA directly. Otherwise, irradiance transposition converts the sensor reading to the module plane, which adds error that grows with the difference in angle. Calculating POA from a sensor oriented more than 30 degrees away from the modules is not recommended. Measured POA can still differ from what the modules receive. The sensor and the modules can respond differently to the angle of incidence and to the light spectrum. How much diffuse sky light the array sees depends on tilt. A horizontal surface sees the whole sky, while a vertical surface sees only half of it. The ground-reflected part is normally small, except where bifacial modules are used. A related term is effective irradiance: the in-plane irradiance the cells actually respond to, after spectral, angle-of-incidence and soiling losses. It is the basis for translating field I-V curve tests.
related_toc1 drafted · lead Direct normal irradiance
Direct beam is one of the three POA components; the beam term on the plane equals direct normal irradiance times the cosine of the angle of incidence.
sec=h2 h=097224a34f0asec=front h=429855123554sec=h30 h=67b7cdd52848c2 drafted · lead Diffuse horizontal irradiance
Diffuse sky light is one of the three POA components; how much of it the array sees depends on tilt.
sec=h2 h=097224a34f0asec=front h=429855123554sec=h4 h=aa0dab698880sec=h8 h=a128b48f86eaGround-reflected light is the third POA component. It is usually small except with bifacial modules.
sec=h2 h=097224a34f0asec=front h=429855123554sec=h1 h=51a013571760sec=h9 h=51a013571760verified by: review-workflowverified on: 2026-10-24
c4 drafted · lead Irradiance transposition
Transposition estimates POA from a sensor mounted at a different orientation.
sec=h2 h=097224a34f0asec=front h=429855123554sec=front h=0dbda907089fsec=h3 h=ab5e834dc829c5 drafted · lead Global horizontal irradiance
sec=front h=429855123554sec=front h=0dbda907089fc6 drafted · lead Clear-sky irradiance model
Modeled clear-sky diffuse irradiance is subtracted and added back during POA transposition.
sec=front h=429855123554sec=front h=0dbda907089fsec=h10 h=3719fb7dc2ccc7 drafted · lead Effective irradiance proposed
Effective irradiance is the in-plane irradiance the cells actually respond to, after spectral, angle-of-incidence and soiling effects.
sec=h29 h=44614856eec2sec=h15 h=2361d5f2450ec8 drafted · lead Bifaciality
The ground-reflected contribution becomes significant with bifacial modules.
sec=h1 h=51a013571760sec=h9 h=51a013571760c9 drafted · lead AlsoEnergy PowerTrack platform and API
PowerTrack can calculate POA from a pyranometer at any orientation.
sec=front h=429855123554sec=front h=0dbda907089fc10 drafted · lead RainWise PVMet weather station proposed
The PVMet 500 reports measured plane-of-array irradiance in W/m² through Modbus registers.
tbl=15.r26 h=8d1a11b14636tbl=6.r4 h=24391a44406etbl=10.r2 h=782815551746review note: support check: partial - The passages show POA irradiance registers in W/m², but none names the PVMet 500 or RainWise.
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