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NREL's PVWatts® Calculator

Estimates the energy production and cost of energy 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.
Notice

We are preparing to update the PVWatts® Calculator and web API to Version 8 later this Fall. This exciting update adds a bifacial module option, a new input for monthly irradiance losses, and updates the photovoltaic module, inverter, and thermal effects models to use more detailed and industry-accepted algorithms. PVWatts® V8 also updates the weather data to 2020 TMY data from the NREL National Solar Radiation Database (NSRDB) for locations covered by the database. (The current NSRDB weather data is from around 2015.) This update will provide production estimates based on the latest, state-of-the art models from NREL that may differ from the current version's estimates, depending on the location and inputs.