Solar & battery
Solar Array Calculator
Array electrical output: voltage, current and power for a given series and parallel arrangement.
Result
The cold open-circuit voltage is the number that damages inverters, and it is checked against the record low for the site rather than a typical winter morning. Exceeding the inverter maximum can destroy it and is not covered by warranty. Panel datasheets give an exact temperature coefficient; the 0.3% figure here is a common approximation for crystalline silicon.
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About this calculator
Why does cold raise the voltage?
Silicon cells produce higher voltage at lower temperature. A string comfortably inside the inverter window on a summer afternoon can exceed it at dawn on the coldest day of the year.
What temperature should I use?
The record low for the site, not an average winter temperature. Design standards specify an extreme minimum precisely because this failure happens once and is permanent.
The formula
string voltage = panels in series x Vmp; cold Voc adds roughly 0.3% per degree C below 25
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