The race among automakers to go green is heating up, and Audi and Volkswagen both just stepped the game up another notch. Not only will the two automakers be partnering with SunPower (NASDAQ:SPWR) to offer rooftop solar to charge their new electric vehicles, they'll be purchasing carbon offsets from 3Degrees to offset emissions from production, distribution, and driving of their vehicles (36,000 miles equivalent for VW and 50,000 for Audi).

Audi is taking its efforts a step further by offering energy storage from SunPower that will provide backup power to a home or electric vehicle to enhance the clean energy offering further.

Audi's A3 e-tron is getting a green boost with solar energy. Photo from 2013 Tokyo Auto Show. Source: Morio via Wikimedia

Going green through the supply chain
The approach by Audi and Volkswagen isn't entirely new in the auto industry. Ford (NYSE:F) and Nissan have partnerships with SunPower to sell rooftop solar systems to electric vehicle buyers. SolarCity (NASDAQ:SCTY.DL) has partnered with BMW, Honda, and of course Tesla Motors (NASDAQ:TSLA), who is its sister company controlled by Elon Musk.

VW's E-Golf at the 2013 LA Auto Show. Source: Wikimedia.

What's different is the carbon offsets and energy storage offering. These would allow electric vehicle buyers to buy a carbon-neutral vehicle and operate it with clean energy, at least on the electric range of the Audi A3 e-tron and VW E-Golf, which can go 31 and 85 miles, respectively, on electric power.

This also increases a growing number of all-electric or electric hybrid vehicles in the market. Finally, consumers looking to cut their carbon emissions have a few options to choose from, and that should only increase in coming years.

Building a challenger to Elon Musk
SunPower's new stable of partners is challenging Elon Musk's own partnership of Tesla Motors and SolarCity. The two are not only working together on signing up rooftop solar customers, Tesla is providing the batteries for SolarCity's energy storage systems. It's a symbiotic relationship that Musk hopes will drive clean energy from the sun all the way to the road.

SunPower residential solar system. Source: SunPower.

For SunPower, partnerships with some of the largest vehicle makers in the world adds to partnerships with 7 of the top 10 homebuilders in the country to install solar. Both channels are attractive for the panel maker because they can be incorporated into the sales and offer both clean energy and cost savings to consumers buying electric vehicles and new homes.

The clean energy revolution marches on
Automakers are clearly seeing the value of going solar, and that creates a big opportunity for both SunPower and SolarCity. As more electric vehicles hit the road they'll be able to expand their customer base and grow brand equity with those demanding cleaner energy solutions. This is an industry investors can buy and watch grow, because we're just at the beginning of a long-term clean energy revolution.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.