I have noticed that many people equate solar panel and battery performance when it gets cold. While lead acid battery performance degrades as the temperature drops, solar panels do the opposite.
For this discussion, I chose the Renogy 100W, Monocrystalline,
12V panel as it seems to be very popular.
All solar panel manufacturers rate their panels based on STC (Standard Testing Conditions). The only spec we are concerned with is the STC Temperature; which is 25C (77F) panel temperature. This is NOT the ambient air temperature. The wattage (Pmax) of the panel, in this case 100W, is measured at 25C.
Panel manufacturers provide temperature coefficients which indicate how their panels perform as the panel temperature rises above or falls below the STC temperature. For the Renogy panel they are:
Temperature Coefficient of Pmax -0.44%/ēC
Temperature Coefficient of Voc -0.30%/ēC
Temperature Coefficient of Isc 0.04%/ēC
Pmax is the wattage of the panel.
Voc is the Open Circuit Voltage of the panel.
Isc is the short circuit Amperage of the panel.
In the below graph I have changed the temperatures from Centigrade to Fahrenheit for better understanding. All the lines cross at 100% and 77F (The STC rating of the panel). But, depending on how hot or cold the panels are the Pmax can either increase to 120% or decrease to 80% of the rated value. So your 100W panel could produce as much as 120W or as little as 80W depending on the temperature. The voltage and amperage perform the same way.
Pat