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Appendix C: How to Read a Datasheet (Annotated)

Module datasheet: what each field means and why you need it

  • Pmax / nameplate watts: STC power; basis of array sizing [Ch 14].
  • Voc: highest voltage; drives the cold-Voc max-voltage check [Ch 15].
  • Isc: highest current; drives conductor/OCPD sizing (×1.56) [Ch 16].
  • Vmp / Imp: operating point; Vmp drives the hot-Vmp MPPT-window check [Ch 15].
  • Module efficiency: watts per area; sets how much fits the roof [Ch 5].
  • Temperature coefficients (β Voc, γ Pmax, α Isc): convert STC ratings to real cold/hot conditions [Ch 4, 15].
  • NOCT / NMOT: realistic operating temperature/output [Ch 4].
  • Maximum system voltage (1,000/1,500 V): ceiling the cold-Voc string total must stay under [Ch 15].
  • Maximum series fuse rating: sets source-circuit OCPD [Ch 23].
  • Mechanical load ratings (Pa): must exceed site snow/wind demand [Ch 25].
  • Dimensions / weight / cell count: layout and structural dead load [Ch 24, 25].

Inverter datasheet: the limits your array must respect

  • Maximum DC input voltage: absolute ceiling vs cold-Voc [Ch 15, 16].
  • MPPT voltage window: array hot-Vmp must stay above its floor [Ch 15].
  • Max input current / # MPPTs / strings per MPPT: bounds parallel stringing [Ch 16].
  • Rated AC output power / max AC current: sets AC side and interconnection [Ch 16].
  • CEC (weighted) efficiency: realistic conversion efficiency [Ch 6].
  • Listings (UL 1741 SA/SB, IEEE 1547): grid-support compliance [Ch 6, 43].