When
shopping for solar panel kits, check out the different ratings. It
is important to know just how a kit will perform before purchasing
it. However, before checking out the different ratings of different
kits, it is important to first know the difference between Standard
Test Conditions (STC) and PVUSA Test Conditions (PV).
For most solar panel kits, the STC rating will be higher than the
PV rating. The STC is a watt-rating used by manufacturers, while a
PTC rating is based on a 1000 watt/m² solar irradiance, 20 degree
Celsius ambient temperature above ground level, and 1 meter/second
wind speed. The PV USA test conditions are much more realistic than
the Standard Test Conditions, therefore it is more important to buy
solar panel kits that have a high PTC rating, rather than an STC rating.
The STC is at 25 degrees Celsius for the cell temperature, but a
silicon solar cell is much more likely to average 20 degrees C above
ambient temperature, just as the PV USA test conditions dictate.
When shopping for solar panel kits, compare the PTC and STC ratings.