That depends on several factors.
1) The size of your system. You can determine how much electricity you want to produce; then size your system accordingly. Note that you can start out small and add on. A system that will generate 100% of your energy needs is expensive, so most systems are sized to generate only a portion of your home’s needs.
2) Your site. If you have a shade-free area from 9 a.m. to 3 p.m., you’ll be able to collect more sun and produce more energy than if your site is shaded.
3) Your region. The more sunny days in your area, the more electricity you’ll be able to generate. For example, systems in the Southwest produce more electricity per year than in the northeast. You can find online calculators to help answer this question in more detail, and installers can provide details about your situation, too.