# pvlib.inverter.pvwatts#

pvlib.inverter.pvwatts(pdc, pdc0, eta_inv_nom=0.96, eta_inv_ref=0.9637)[source]#

NREL’s PVWatts inverter model.

The PVWatts inverter model 1 calculates inverter efficiency $$\eta$$ as a function of input DC power $$P_{dc}$$

$\eta = \frac{\eta_{nom}}{\eta_{ref}} (-0.0162\zeta - \frac{0.0059} {\zeta} + 0.9858)$

where $$\zeta=P_{dc}/P_{dc0}$$ and $$P_{dc0}=P_{ac0}/\eta_{nom}$$.

Output AC power is then given by

$P_{ac} = \min(\eta P_{dc}, P_{ac0})$
Parameters
• pdc (numeric) – DC power. Same unit as pdc0.

• pdc0 (numeric) – DC input limit of the inverter. Same unit as pdc.

• eta_inv_nom (numeric, default 0.96) – Nominal inverter efficiency. [unitless]

• eta_inv_ref (numeric, default 0.9637) – Reference inverter efficiency. PVWatts defines it to be 0.9637 and is included here for flexibility. [unitless]

Returns

power_ac (numeric) – AC power. Same unit as pdc0.

Notes

When sourcing pdc from pvlib functions (e.g. pvlib.pvsystem.pvwatts_dc()) their DC power output is in W, and pdc0 should have the same unit (W).

Note that pdc0 is also used as a symbol in pvlib.pvsystem.pvwatts_dc(). pdc0 in this function refers to the DC power input limit of the inverter. pdc0 in pvlib.pvsystem.pvwatts_dc() refers to the DC power of the modules at reference conditions.

References

1