The Solar Investment Tax Credit, part of the Energy Policy Act of 2005, offers a tax credit equal to 30% of the cost of eligible solar system parts and installation. The actual cost to you is the installed cost minus these tax credits which are like income tax refunds to you. Richmond, Virginia receives 4.13 hours of peak sun per day on average all year long. Suppose you live in Richmond and purchase a 5 kW PV systems for $15,000 installed. Your utility will install a two-way connection to the grid, so you draw off power when you aren't producing enough for your household, at night for example. The utility keeps track of what you put into the grid and what you draw out of the grid. If you draw out more than you put in, they charge you about 12/kWh. If you put in extra, let's assume you don't get anything in return (for simplicity, although it's a little more complicated than that). How many years will it take to payback the cost of the system