Short-circuit current, written Isc, is the current a PV module or string delivers when its output terminals are shorted together. It is one of the main values on the I-V curve, along with open-circuit voltage, maximum power voltage, maximum power current and maximum power. Module datasheets state Isc at standard test conditions, and conductor ampacity for PV source circuits is sized from this rated value, using 125% of the summed parallel Isc ratings. Isc is proportional to the irradiance on the array, so field measurements should be taken in clear sky on clean, unshaded modules, and strings compared with each other should agree within 5%. To test, the string is isolated and briefly shorted with a rated PV tester, shorting cable or switch box. The current is read with a rated clip-on or in-line ammeter, and the short is interrupted with a load break device before anything else is changed. Isc is also used to work out the fill factor, which is maximum power divided by the product of Voc and Isc. A low fill factor can point to faults that cost energy yield. For amorphous silicon modules, the ratio of Isc to irradiance changes with air mass and with the direct and diffuse light components because of spectral response.
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related_toc1 drafted · lead I-V characteristic curve
Isc is one of the key values read from a string I-V curve measurement, alongside Voc, Vmpp, Impp, Pmpp and fill factor.
tbl=4 h=dbeab86d1089tbl=4.r5 h=8404bef4b055c2 drafted · lead Fill factor
Fill factor is maximum power divided by the product of open-circuit voltage and short-circuit current.
sec=h24 h=69690a32e377c3 drafted · lead Open-circuit voltage
Voc and Isc together form the denominator of the fill factor.
tbl=4 h=dbeab86d1089sec=h24 h=69690a32e377c4 drafted · lead Standard test conditions
The module Isc rating is stated at STC.
tbl=8.r2 h=c41b4ab035d5sec=h97 h=e749cb64574dRequired source circuit conductor ampacity depends on the rated module short-circuit current; maximum PV source circuit current is 125% of the sum of parallel module Isc ratings per NEC 690.8(A).
sec=h97 h=e749cb64574dc6 drafted · lead Plane-of-array irradiance
Array short-circuit current is proportional to the solar irradiance on the system.
sec=h17 h=aa38e0df17e3For amorphous silicon modules, the short-circuit response Isc/G varies with air mass because of spectral response.
sec=3.2.2 h=cc128f301ebec8 drafted · lead String short-circuit test proposed
Field test that temporarily shorts an isolated PV string and measures Isc to confirm correct operation.
sec=6.5.2 h=c32ca77081a9sec=h17 h=aa38e0df17e3sec=6.5.2.2 h=e78cd394ec93c9 verified · fact Clamp meter
A suitably rated clip-on ammeter can measure string short-circuit current during the test.
sec=6.5.2.2 h=e78cd394ec93verified by: review-workflowverified on: 2026-10-24
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