Solar Temperature Derating Calculator
Estimate module output under real operating conditions by modeling cell temperature from ambient, irradiance, wind, NOCT, and mounting type.
- Enter module and coefficient data Input module STC wattage and Pmax temperature coefficient from the datasheet.
- Set environmental conditions Enter ambient temperature, irradiance, wind speed, and module NOCT.
- Choose mounting condition Select flush roof, open rack, or ground mount to apply thermal mounting adjustments.
- Calculate real output Run the tool to get estimated cell temperature, adjusted output watts, and loss versus STC.
Why do solar panels produce less than nameplate in summer heat?
Nameplate is measured at 25 C cell temperature. Hotter cells reduce voltage and output; this tool applies the module temperature coefficient to estimate that derate.
What is NOCT and where do I find it?
NOCT is nominal operating cell temperature measured under standardized field-like conditions. It is listed on module datasheets and used for temperature modeling.
Does roof mounting really make a big performance difference?
Yes. Flush-roof arrays usually run hotter than open-rack systems, which increases temperature losses. The calculator includes mounting offsets for this effect.
Can wind improve panel output?
Yes. Wind cools cells and lowers operating temperature, which can recover some power otherwise lost to heat.
Should I model at 1000 W per square meter all year?
No. 1000 W/m² is an STC reference point. Real irradiance varies by weather, season, and sun angle, so run scenario checks with expected site conditions.
Is this enough to estimate annual production?
It is useful for condition-based snapshots. Annual energy forecasting still needs hourly weather data and full system-loss modeling.