PerformanceUp to date · Jan 15, 2026
PTC Rating
PVUSA Test Conditions rating — a more realistic solar panel power rating using 1,000 W/m2 irradiance but 45 degrees C cell temperature (vs 25 degrees C for STC). PTC is typically 88-92% of STC.
Why It Matters
PTC gives a more honest picture of panel output in warm real-world conditions. CEC uses PTC ratings for California rebate calculations.
Related Terms
Standard Test Conditions (STC)
The standardized laboratory conditions under which solar panels are rated: 1,000 W/m² irradiance, 25°C cell temperature, and AM 1.5 spectrum. Panel wattage ratings are always at STC.
Cell Temperature
The operating temperature of solar cells under sunlight, typically 20-40 degrees Celsius above ambient temperature. Higher cell temperatures reduce voltage and power output.