The cost per watt makes it easier to compare prices between quotes and gives you a better idea of how fairly the system is priced. The average price of solar is about $2.14 to $3.22 per watt in Fairfield, so anything in that range is a fair price. After the federal solar tax credit, the final cost will drop by 30%, down to $15,000 for a 9.18 kW system. Solar is a growing industry that attracts contractors from many backgrounds—sometimes only loosely related to solar.