The smaller ones are tougher. When you're siting a large wind farm you can stick it where the best winds are and you also have to be near transmission lines. When you're dealing with small turbines you don't have that luxury, because you can't string 20 miles of line to a community since that will ruin the economics. So you're generally more constrained; you have to site them near to where the load is, and there you're looking at capacity factors that are more around 25%.
On March 24th, 2009. See this statement in context.