That space can be used for other things too though such as grazing livestock.

Relatedly, Elon Musk claims that if you cover the area used up by a Nuclear plant with solar panels than you can get equal power production. The actual reactor is small, but the security etc. means that there's a large boundary zone. Plus of course no-one wants to live near one.

On sunny days, or on average?

Even countries who have no unused land, like the Netherlands and Belgium, have managed to build big wind farms. They've mostly placed them offshore.

In the Netherlands at least, onshore is far bigger than offshore: roughly 90% by capacity, 85% by production.

Detailed stats are here: http://statline.cbs.nl/Statweb/publication/?DM=SLNL&PA=70802...