Flat fraction

Method

The loss is the same fraction of the inverter output at every load. On a timestep the inverter draws its night consumption, the fraction of that consumption is drawn as well. The transformer and the later AC losses act on the output after this loss. This is the AC wiring loss of SAM's detailed photovoltaic model.

The math

$$L_{ac} = f_{ac}\,\lvert P_{out} \rvert \tag{1}$$

where

Symbol	Meaning	Unit
$L_{ac}$	the AC cable loss of one inverter	W
$f_{ac}$	the AC wiring loss, a fraction	—
$P_{out}$	the inverter's AC output, negative while it draws its night consumption	W

References

1. NREL SAM Simulation Core (SSC) source code, release 2026.7.3, github.com/NatLabRockies/ssc: ssc/cmod_pvsamv1.cpp, the AC wiring, transformer and transmission losses in exec(); shared/lib_power_electronics.cpp, Transformer::transformerLoss()

API

ac_losses.ohmic_model = flat

Symbols follow the symbol registry.