Annual Energy is measured in kilowatt-hours (kWh). This annual sum is the amount of DC power that solar panels on the building surface will create given the solar radiation levels and sky conditions from the weather file, and the surface orientation and obstruction shading characteristics of the model for every hour of the year. If 60 percent of the surface is shaded by other parts of the building, then the remaining 40 percent is used for photovoltaic calculations.
The Potential Cost Savings and System Payback calculations are based on the Annual Energy production the Applied Electric Cost, and the future cost escalation only. Energy incentives, tax breaks, and loan solutions are not taken into account. Incentives can lower the payback period significantly, so the payback figures are fairly conservative.
For more information on incentives in the United States, refer to the following website: http://www.dsireusa.org.