PVWatts
Calculates energy production estimates for photovoltaic systems from location data.
Read docs Updated 2026-06-17
What is PVWatts?
PVWatts is a calculation service that determines expected energy yields for photovoltaic arrays using site latitude, longitude, and associated climate inputs.
It is used by solar project developers, engineers, and analysts to evaluate potential output at specific locations before system deployment.
What you can build with PVWatts
Solar project feasibility calculator
Embed PVWatts calls in web apps to instantly estimate annual kWh output and payback for user-specified rooftop systems at any US address.
Utility-scale site screening tool
Batch-query multiple lat/long points to rank potential solar farm locations by expected capacity factor and monthly production profiles.
Home energy dashboard integration
Pull PVWatts estimates into smart-home or utility apps so homeowners can compare their actual solar generation against modeled performance.
Get started with PVWatts
- 1Sign up at developer.nrel.gov and obtain a free API key
- 2Read the PVWatts v5 endpoint documentation
- 3Build a GET request with required params (lat, lon, system_capacity, etc.)
- 4Append your API key as a query parameter and send over HTTPS
- 5Parse the JSON response for ac_annual, ac_monthly and other production values
PVWatts: pros & cons
Pros
- +Free with generous rate limits
- +Well-validated NREL simulation engine
- +Returns both annual and monthly/hourly energy estimates
- +Supports common PV system configuration options
Cons
- –Primarily validated for United States locations
- –No real-time weather or live production data
- –Requires many input parameters for accurate results
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Frequently asked questions
A free NREL service that estimates photovoltaic energy production for locations and system specifications.
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