Unlike traditional energy sources, such as oil, coal and hydroelectric, solar panels can be put anywhere, specifically, in places that would be otherwise unusable. Solar panels on buildings take up no land at all, but take advantage of land being used for buildings. Additionally, solar panels can be put on land that is not arable, such as desert or otherwise degraded land.
Solar energy does not use a reasonable amount of land. When people put solar panels on land, they are using some land up, but that was probably land that was not going to used for any thing important. In Arizona, they put solar panels in the desert because that land is really not used for any thing.