The next time you catch a Discount Cab in Phoenix or Tucson, you can rest assured your taxi is “green” (even if it is red, white, blue or yellow) thanks to a recent installation of $750,000 worth of solar panels.

The cash outlay comes from Discount Cab parent company, Total Transit, Inc., and the 400 panels are arranged on top of the roof of its Glendale, Arizona headquarters on Camelback Road. Glendale is a suburb about 10 miles from downtown Phoenix.

The panels, each providing 230 watts of power, reportedly supply all the electricity needed by the company in the winter, and most of juice needed in the summer as well. It is also one of the largest solar installations in the Phoenix metropolitan area.

According to Total Transit executives, the solar system will reduce carbon emissions by 377 tons per year, which is the same as planting 9,700 trees or taking more than 72 cars off Arizona roads.

The system was installed by Phoenix-based PerfectPower Inc., a privately owned design-build solar firm comprised of Phoenix residents and led by CEO Lynn Paige. In 2007, PerfectPower was recognized by the Arizona Small Business Association in collaboration with the Edward Lowe Foundation as one the “Arizona Companies to Watch”. PerfectPower was also named No. 31 of the “Top 50” fastest-growing women-owned/women-led privately-owned businesses in the United States and Canada by The Women Presidents’ Organization (WPO) and Entrepreneur Magazine.

In 2009, PerfectPower was responsible for the 2.1-kilowatt solar installation at the William R. Sullivan Elementary School in Phoenix. Together with Earth Day Network and the University of Phoenix Foundation, the Feb. 6 installation will allow the Sullivan School to save more than $120,000, and avert the production of 166,800 pounds of carbon dioxide, over the next 30 years.

Total Transit currently operates the largest fleet of Toyota Prius taxis in the nation, so its footprint is already greener than most. Total is closely followed (or perhaps even matched) by Clean Air Cab of Phoenix, whose 27 Hybrid Prius cabs hit the streets on October 19, 2009. And both are followed, albeit not very closely, by Broadway Cab of Portland, Oregon, which in 2008 replaced six of its combustion-engine vehicles with Toyota Prius hybrids.

Other than these three – and only one, Total Transit, has solar-powered bragging rights – the U.S. taxicab business is pretty grimy, in more ways that one. Fortunately, both cities mentioned (Phoenix and Portland) are going solar in other ways. Phoenix, for example, has 766.8 kilowatts of installed solar, and Portland boasts 132 solar installations, for 319 kilowatts of solar power, 80 percent of them in the 10-25 kilowatt range.