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

\[P_{ac} = \min(\eta P_{dc}, P_{ac0})\]
  • 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]


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


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.



A. P. Dobos, “PVWatts Version 5 Manual,” http://pvwatts.nrel.gov/downloads/pvwattsv5.pdf (2014).