_Where_ is relevant. Point is every kilowatt of solar electricity you use is 1-10 m^2 of ground denied that energy. If the collector is on top of your house, fine - probably will help with your home cooling (gettin' hot here in GA), but over other space you've just deprived a nano-ecosystem its energy supply (no big deal for home use, but significant when it's upwards of a couple thousand square miles).