Size PV strings against your inverter's voltage and current limits, with cold-weather Voc correction by temperature coefficient or AS/NZS 5033:2021 Table 4.1. Enter the module datasheet values and the results update as you type.
Enter coefficients exactly as the datasheet shows them, e.g. −0.25. γ is used for hot-weather Vmp; leave it blank to fall back to β.
Table 4.1 applies to crystalline and multi-crystalline silicon modules when the Voc temperature coefficient is not available. The factor is picked automatically from the lowest expected temperature below.
Bifaciality raises current only — string voltages are unchanged. Maximum string current becomes 1.25 × KI × Isc (Clause 3.3.3.1).
Close-parallel roof — modules close and parallel to a tiled roof see very limited rear-face light, so KI = 1. (Appendix J(c))
Datasheet BNPI Isc — where no simulation data exists, KI = Isc BNPI / Isc. BNPI is the bifacial nameplate irradiance condition: 1000 W/m² front + 135 W/m² rear (Clause 1.3.3). (Appendix J(b))
Simulation — KI from a simulation accounting for albedo, location, orientation, shading, row spacing, bifacial factor and mismatch. (Appendix J(a))
Where both faces can see irradiance above 400 W/m² — fence-type or vertical installations, and open racks in snowy areas — the standard recommends determining KI by simulation.
Use the record low for the site (daytime module temperature can reach ambient at sunrise). 70 °C cell temperature suits most ventilated rooftop arrays; use 75–80 °C for poorly ventilated mounting.
| Lowest expected temperature | Voc correction factor |
|---|
Applies to crystalline and multi-crystalline silicon modules where the manufacturer's Voc temperature coefficient is not available. Where the coefficient is available, the coefficient method gives the exact figure and should be preferred.