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.

Solar Temperature Derating Calculator

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.

Run the numbers for your project

Use the Solar Temperature Derating Calculator to get an exact answer for your inputs.

Open the calculator

Is this enough to estimate annual production?

Run the numbers for your project

Related questions

Pro launch updates