The national average installed cost is $2. For a typical 8 kW residential system: $20,000-$30,000 gross, $14,000-$21,000 after the 30% federal ITC. solar calculator — enter your ZIP code and electricity bill, and it returns your recommended system size in kW, the number of panels, the roof area you need, the gross install cost, the annual savings, the payback period, the 25-year lifetime profit, and the CO₂ offset. Built on. Installed cost per watt including panels, inverter, mounting, wiring, labor, and permits. Federal ITC %? Federal Investment Tax Credit. This is a dollar-for-dollar reduction in taxes owed, not a refund. Understanding solar costs. The typical home requires about 12 kilowatts (kW) of solar energy to meet its electricity needs, which costs an average of $30,505 before incentives, according to EnergySage data. Depending on where you live, state and local programs can knock thousands off that price, and if you finance with a. If you select to hire a contractor to install your solar kit, you should expect to pay approximately $1. 00 per watt for labor, wire, conduit, fittings, breakers and other miscellaneous electrical components to complete the solar system installation.