Effects on PV System Output#

Loss models#

pvsystem.combine_loss_factors(index, *losses)

Combines Series loss fractions while setting a common index.

pvsystem.dc_ohms_from_percent(vmp_ref, ...)

Calculates the equivalent resistance of the wires from a percent ohmic loss at STC.


snow.coverage_nrel(snowfall, poa_irradiance, ...)

Calculates the fraction of the slant height of a row of modules covered by snow at every time step.

snow.fully_covered_nrel(snowfall[, ...])

Calculates the timesteps when the row's slant height is fully covered by snow.

snow.dc_loss_nrel(snow_coverage, num_strings)

Calculates the fraction of DC capacity lost due to snow coverage.

snow.loss_townsend(snow_total, snow_events, ...)

Calculates monthly snow loss based on the Townsend monthly snow loss model [1]_.


soiling.hsu(rainfall, cleaning_threshold, ...)

Calculates soiling ratio given particulate and rain data using the Fixed Velocity model from Humboldt State University (HSU).

soiling.kimber(rainfall[, ...])

Calculates fraction of energy lost due to soiling given rainfall data and daily loss rate using the Kimber model.


shading.masking_angle(surface_tilt, gcr, ...)

The elevation angle below which diffuse irradiance is blocked.

shading.masking_angle_passias(surface_tilt, gcr)

The average masking angle over the slant height of a row.


The diffuse irradiance loss caused by row-to-row sky diffuse shading.


spectrum.spectrl2(apparent_zenith, aoi, ...)

Estimate spectral irradiance using the Bird Simple Spectral Model (SPECTRL2).


Generate a generic smooth spectral response (SR) for tests and experiments.


Read the ASTM G173-03 AM1.5 global spectrum on a 37-degree tilted surface, optionally interpolated to the specified wavelength(s).

spectrum.calc_spectral_mismatch_field(sr, e_sun)

Calculate spectral mismatch between a test device and broadband reference device under specified solar spectral irradiance conditions.