For more than a year, we’ve been supplying Solar Today Magazine with monthly ‘PV Power Maps’ for its regular column. Not only are these maps gorgeous to look at, but they provide very interesting insight into how solar resources in the U.S. translate into actual power produced.

PV Power Map - 10.12

That’s because the maps go beyond simply depicting the amount of sunshine (or more precisely ‘irradiance’ or ‘insolation’) a particular location receives during a given month. The PV Power maps show the amount of electricity that could have been generated by a nominal* 1-kilowatt (kW) photovoltaic (PV) system during that timeframe. The power data is generated from SolarAnywhere® irradiance data using the PV simulation engine that powers many of our products, including Clean Power Estimator®, WattPlan®PowerClerk®, SolarAnywhere® FleetView® and SolarAnywhere® SystemCheck®.

The PV Power Map makes it easy to estimate what the output of a solar system might be in your area. This information can be used to benchmark a system you have already installed, or give you an idea of how much electricity a PV system could provide. Simply pinpoint your location on the map, refer to the color chart to determine that month’s PV power output, and multiply that number by the kW value of your system.

Here are a couple of examples using the October 2012 map as seen above:

  • In October, a 1 kW PV system in San Francisco or Dallas would have produced approximately 110 kWh. Therefore, a 3 kW PV system in either location would have generated approximately 330 kWh of electricity (3 kW system X 110 kWh = 330 kWh produced).
  • Similarly, a 4 kW system in Chicago or Washington, D.C., would have generated approximately 360 kWh (4 kW system x 90 kWh = 360 kWh produced).

To get an idea of what a PV system in your area might produce over time, it’s important to look at data over a year or more, as the power production can vary widely from month to month – particularly in the Northern states and coastal areas where seasons affect irradiance levels. An example of how storms can impact production levels can be seen in the map below, which compares the same nine-day period in 2011 and 2012 that coincided with Hurricane Sandy.

PV Power Map - Hurricane Sandy

You can access PV Power Maps for the entire year at, or on page 8 of each issue of Solar Today Magazine. You can also access free historical irradiance data at

* What is a ‘nominal’ system? Here’s the fine print: The PV Power Map is created with power output estimates generated by SolarAnywhere simulation capabilities and hourly satellite-derived irradiance data with spatial resolutions from 1 to 10 kilometers. The calculations are based on a PV system with a total 1-kW nameplate rating that is configured as five 200-watt PV panels with a 1.5-kW inverter; fixed, south-facing panels with 30 degree tilt; no shading; panel PVUSA Test Conditions rating of 178 watts; and inverter efficiency of 95.5 percent.