An electric car isn't nearly as eco-friendly as it sounds, if the electricity it runs on is generated from eco-unfriendly sources like natural gas or coal. Together, those fossil fuels currently provide roughly two-thirds of the country's energy.

Fortunately, Ford (NYSE: F) and SunPower (Nasdaq: SPWRA) have teamed up to hopefully ensure that the new Focus Electric, entering production later this year, will run on clean solar power. The companies have introduced a "Drive Green for Life" program that allows customers to pay roughly $10,000, after federal tax credits, for a 2.5-kilowatt rooftop solar-power generator that can generate enough electricity to fuel the Focus Electric for roughly 1,000 miles of driving per month. Evidently, joint ventures are all the rage in solar nowadays.

SunPower systems will be available directly through Ford dealerships, which won't directly profit from the sales. Since SunPower currently only has 400 dealers, adding Ford's vast network of dealerships will greatly broaden the company's reach. Ford also now has an agreement with electronics retailer Best Buy (NYSE: BBY) to sell 240-volt home charging stations for the Focus Electric.

Ford is making strides to catch up with General Motors' (NYSE: GM) Chevy Volt, which hit the market first. However, the Volt is merely a plug-in hybrid, rather than a full-fledged electric car. The Nissan Leaf is the closest competitor as a mainstream all-electric car. I wouldn't include Tesla Motors (Nasdaq: TSLA) on the immediate competitor list quite yet. Its current pricey Roadster is far from mainstream, while the more affordable Model S won't hit the road until next year.

I think this deal is great for both Ford and SunPower, although weighted a little bit more in the latter's favor. SunPower gets to expand its distribution network substantially, and market directly to exactly the right crowd: eco-conscious early adopters who value alternative energy sources. Ford will benefit to the extent that it can boost Focus Electric sales by packaging the car with a complementary offering. This deal validates solar-powered electric cars' progress toward the mainstream, which should reward patient investors who are willing to stick it out for the long road to sustainability.