How to Calculate Solar Power Potential
Thinking of installing a solar panel array to generate electricity? Find out how many kilowatts it can produce and at what cost, anywhere in the United States, by using the Department of Energy's free online solar potential calculator, IMBY. You'll get unbiased answers to these basic questions, as well as expected electric bill savings and your project's payback period. Use IMBY to model your solar project, get a handle on its economics, and generate estimates to use when talking to contractors or vendors. Does this Spark an idea?
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Instructions
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Initial Inputs
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Open the IMBY calculator (see References). It has a Google map of the United States in the left pane and three tabs to its right in the "Options" pane that are labeled "Location," "Solar" and "Wind."
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On the "Location" tab, enter a property address. Click the "Find" Button to open an aerial image of the property, identified by a green stick pin, in the map pane.
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Back in the Options panel, select "Solar" as the energy type, which opens the "Solar" tab.
Draw your Solar Array
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Click the Solar tab's "Draw" button. Now hover your mouse cursor over the property. Mouse-click once to establish the solar array's first corner. A small blue circle will surround the cursor's point.
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With the cursor draw a light-blue line and stop with a click where you want to fix the array's second corner. From this point, draw a second, angled line to where you want the third corner. Again, click to fix the point. Repeat to make the fourth corner.
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Draw a line from the fourth corner back to the array's starting point. Double-click to stop drawing. Your planned array should now be superimposed on the property as a closed, blue geometric shape.
Simulate Solar Potential
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Check the data now populating the five "Inputs" boxes on the "Solar" tab's lower right pane. Change the tilt angle with your roof's angle if you plan to build the array on a pitched roof. Twenty degrees is typical for U.S. roofs. Leave the azimuth at 180 degrees; it points the array due south for maximum daily sun exposure.
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Click "Run" on the "Solar" tab. This opens the array's payback data on a new "Summary" page. You can re-run the data with, for example, differing rebates or tax incentives.
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In the right pane, under "Select a Load Profile," choose the nearest metropolitan area or input a custom load profile. (Click "Help" for an explanation.) Click "Run Load Profile" and you open a projected utility bill. If necessary, adjust the buy-back rate (what the utility will pay for surplus electricity) and/or the current electricity rate and recalculate.
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Tips & Warnings
Re-run the simulation as often as you wish, from scratch, or with refined data, such as individualized costs and buy-back rates from an electric bill or utility's customer service. Save each run with IMBY's "Export" feature for spreadsheet comparison later on. (Requires a spreadsheet program.)
Consider IMBY a starting point and consult a reliable solar professional to refine the model with answers to questions such as "How will surrounding structures or shade trees affect my array's solar azimuth?"
