0.1367 watts per square centimeter x 30% /4 (for ecological inefficiencies) = .0103 watts/cm^2 on a sunny day, that's how much.
A 1000m x 1000m array, even with the inefficiencies of ground-based solar power (clouds, oblique angle of sunlight, that little thing called nighttime), could generate 100 megawatts at that efficiency.
The rule of thumb is that 100,000 people need 50 megawatts.
The real advantage is in decentralization, however.
Five square meters would supply the needs of a typical American household...55 square feet, a 5'x 11' grid.
Alas, it's not quite good enough for solar-powered autos, but every two hours of charge would get you one hour of travel as speedy as you are accustomed to, good enough to supplement drawing off of city current..or paying for gasoline for your hybrid.