Derate factor calculator

Enter each loss as a percentage of the energy left after the one before. The ten names follow the PVWatts list. Presets are the documented PVWatts defaults and invented examples, not measurements for any site. Use a decimal point or a decimal comma, such as 0,5.

Soiling, %

Shading, %

Snow, %

Mismatch, %

Wiring, %

Connections, %

Light-induced degradation, %

Nameplate rating, %

Age, %

Availability, %

Optional: DC energy before losses, kWh a year (invented 10,000)

Optional: inverter efficiency, % (separate from the derate)

Overall derate (multiplied): -

Overall loss (multiplied): -

Ten percentages added: -

Energy after derate, multiplied: - kWh. Added: - kWh.

AC energy after the inverter: - kWh

The added figure is shown only to show the error. Use the multiplied one. Clipping, temperature and reflection are not in this calculator.

Check a quoted derate

Derate in a quote, as 0.86 or 86%

Loss the quote implies beyond your ten entries: -

Convert an old-style derate

Derate that includes the inverter, such as 0.77

Inverter efficiency, %

Implied DC system loss, with the inverter taken out: -