NREL's PVWatts® Calculator
Estimates the energy production of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations.
PVWatts® V8 adds several new features, including a bifacial module option, a new input for monthly irradiance losses that can be used to represent soiling or snow losses, and updated models for the photovoltaic module, inverter, and thermal effects that use more detailed algorithms than older versions. Version 8 uses new weather data from the NREL National Solar Radiation Database (NSRDB) PSM V3 TMY 2020 dataset. PVWatts® V8 provides production estimates based on the latest, state-of-the art and industry-accepted models from NREL that may differ from the previous version's estimates, depending on the location and inputs.