Photovoltaics Economics Calculator

Web-based tool which allows you to describe your solar system in detail and provides a detailed breakdown of what sort of power you'll get out of it and how economical of a investment the system will be. It uses the TMY2 solar data from the NREL Renewable Resource Data Center. This calculator allows users to customize their setup, providing greater feedback on how much power is provided when, and most importantly, a detailed economics breakdown of how the investment works out. It also keeps track of battery charge states for off-grid users. Screen Shots


solar, photovoltaic, economics


Validated against PVWatts, a widely recognized solar power output calculator. When given the exact same conditions, power production is generally within a few percent of PVWatts results.

Expertise Required

Low. All terms used in the page are defined, and if the user doesn't know a value, it can be left as the defaults.


Web-based with numerous users.


The general public, people who are considering an investment in solar power and want to know what they'll need and whether it makes economic sense.


All inputs that can be provided can be seen on the web page. The only mandatory inputs are state and city.


Output shows up on the same page after a momentary delay whenever the user changes a field (asynchronous display).

Computer Platform


Programming Language

Asynchronous C++ CGI and Javascript.


Provides detailed breakdown of how solar would work out for an individual's custom setup.


Does not consider the environmental benefits of solar over more polluting sources. To assign an environental cost to grid power, artificially raise the price per kilowatt hour of power bought from and sold to the grid. This calculator also assumes that energy costs remain roughly constant despite inflation due to advancing technology. Degradation of cells over time is also not considered.



Daughters of Tiresias


United States




Free web-based