NLR's PVWatts® is a web application developed by the National Laboratory of the Rockies (NLR) that estimates the electricity production of a grid-connected roof- or ground-mounted photovoltaic system based on a few simple inputs. To use the calculator, you provide information about the system's location, and basic design parameters. PVWatts® calculates estimates of the system's annual and monthly electricity production.
Important Note. PVWatts® is suitable for very preliminary studies of a photovoltaic system that uses modules (panels) with crystalline silicon or thin film photovoltaic cells. PVWatts® production estimates do not account for many factors that are important in the design of a photovoltaic system. If you are using PVWatts® to help design a system, you should work with a qualified professional to make final design decisions based on an assessment of the system location and using more detailed engineering design and financial analysis tools.
To get started with PVWatts®, type the street address, zip code, or latitude and longitude of the system's location, and click GO. PVWatts® uses this information to automatically identify solar resource data available at or near the system's location. For example, for a system on the NLR campus, you could type any of the following:
The calculator estimates the monthly and annual electricity production of a photovoltaic system using an hour-by-hour simulation over a period of one year. To represent the system's physical characteristics, PVWatts® requires values for six inputs:
You can refine the system design assumptions with three optional advanced inputs:
PVWatts® estimates the monetary value of the electricity based on an annual average retail electricity rate.
If you would like to send NLR feedback about PVWatts®, click Feedback at the top of the PVWatts® page and email us your question or comment.
PVWatts® is one of several tools available from NLR for analyzing and modeling renewable energy projects. See NLR Data and Tools for information about these tools.