To increase the use of solar on parking garages, cities can incorporate solar panels into the parking requirements for commercial developments. The legal basis for requiring solar panels atop a parking lot, according to Shoup, is similar to the basis for requiring the parking lot itself - to mitigate an impact. If a development increases the demand for scarce energy during peak hours, the solar requirement for the parking lot will help to meet this peak-hour demand.
Shoup says that California’s Million Solar Roofs program provides generous subsidies for solar panels, and the federal government offers additional tax credits, so developers won’t have to pay the full cost of a city’s solar requirement.
In addition Shoup says solar arrays are highly visible evidence of a company’s commitment to the environment.
Google has installed solar canopies on its parking lots to satisfy 30 percent of its headquarters’ power demand.
Envision Solar is just one of the companies providing such services. See their site for more info on “solar groves” over parking lots.