...roof top installations are the most challeging ones in such locations , it depends always on the clients needs and his will of spending more or less for having his expected solar gains met.
So this is something the installing company has to clear in the first meeting before making the plans for the installation, but anyway the installation on the ground is mostly a thing used to gain both electricity and a bit more of shade in this sunny regions, like I wrote before it´s a decission which the client has to take.