[wmertens]

Power goes up exponentially with size. To get good RoI, you need to go huge.

[divbzero]

Power is roughly proportional to the wind turbine’s cross sectional area. So power scales by the square of blade length but isn’t quite exponential.

[flavius29663]

It's more than squared, it's cubed. If you consider height advantages, it's going to produce 22 times more energy for each doubling of the blade length. http://large.stanford.edu/courses/2011/ph240/parise1/

[Tuna-Fish]

And not only is there more output, it's more valuable per unit.

Higher winds are much more stable. Both in having less completely still days, and having the median be much closer to the maximum. A wind turbine that is built big enough starts having a large part of it outbut be effectively baseload instead of intermittent, and as more renewables are built out, baseload capacity is increasingly more valuable than intermittent.

[Grustaf]

Yes, it's not exponential at all. Larger blades also need to be thicker, and the tower stronger etc. But still, it's economies of scale like everywhere else.

[Tuna-Fish]

It's more than square, because bigger also means taller which means more wind.