The sun delivers 103 Wm-2 of Electromagnetic flux on the earth’s surface. The total power that is incident on a roof of dimensions 6m × 30m, is

1.8 × 105 W 7.2 × 105 W 0.9 × 105 W 4.5 × 105 W

1.8 × 105 W

$P = IA = 10^3 \times 180 W = 1.8\times 10^5 W$