Walmart is adding five more stores to its solar-energy pilot program - but not because management's turned into a bunch of tree-hugging Arkansas hippies. The megastore multinational is going green for the sake of green - money, that is.

The five latest stores in Walmart's pilot program, which now totals 20 stores, Sam’s Clubs, and distribution centers in Hawaii and California, will all be located in sunny Puerto Rico. Their solar installations will be provided by SunEdison, described by Walmart as being "North America’s largest solar energy services provider."

Walmart, however, won't be buying the solar systems from SunEdison. Instead, that panel punter will finance, own, build, and operate them itself, and sell the generated juice to Walmart. The systems will provide the stores with 25 to 35 per cent of their electrical needs, and are projected to produce 90 million kWh of power over the 15-year life of the project.

Walmart is dead serious about solar power, stating in their most recent Solar Power Fact Sheet that "our goal [is] 100 percent renewable energy."

The company's current 20 installations are expected to produce 16 to 18 million kWh this year - and there are more to come. This April, Walmart forged a deal with BP Solar to install panels on an additional 10 to 20 Walmart facilities in California by 2011, which the company says will generate between 8 and 16 million kWh annually.

According to the US Environmental Protection Agency's calculations, this expansion will prevent more than 10,000 metric tons of carbon dioxide from mucking up the atmosphere each year.

Those are hefty numbers, but they're a mere drop in the proverbial bucket compared to what Walmart might eventually achieve. Jason Mick over at DailyTech estimates that if Walmart were to solarize all of its facilities, the resulting installations would total 35 square miles of panels that would produce a cool three gigawatts of power.

However, while Walmart's dedication to solar power may seem impressive, the EPA ranks them only 15th among the US's top 25 green corporations.

At the top of that list is Intel, which buys offset credits equivalent to 1.3 billion kWh, or 46 per cent of its total power needs. Will Swope, Intel's VP for corporate sustainability, told Scientific American that Intel shareholders support the offset-credit program. "Economics have shown," he says, "that companies that maintain a more sustainable footprint have done better - even in economic meltdown - than those that don't."

Intel, by the way, is also spending a chunk of its cash reserves on green tech. At this Wednesday's Technology Summit in San Francisco, Steve Eichenlaub of the company's Intel Capital investment group announced investments in five "cleantech" companies.

Eichenlaub also described the group's cleantech focus as "meant to embrace how Intel has appreciated how what we do from a technology, architecture, and solutions standpoint can have a major role in making the policy, the efforts of the industry, and enabling new business models to address issues such as global warming."

Make no mistake, however - neither Walmart, Intel, nor any of the other companies in the top-25 list are moving to sustainable energy or investing in cleantech out of the goodness of their corporate hearts. They're doing so either to save money - Walmart - or to make money - Intel.

Some of those green greenbacks will be realized immediately, and some down the road. Intel's strategic cleantech investments, for example, are helping build an industry that will require massive IT investments - investments that will help fatten Intel's bottom line.

Intel thus benefits doubly: on a pure cash basis when they buy into a company early and then sell their stake when its value rises, and on an indirect basis when its entire cleantech portfolio births an industry sector with a ravenous hunger for compute power.

Walmart's benefits are more immediate. The company's energy director, David Ozment, recently told USA Today that Walmart was already enjoying "moderate savings" in its pilot projects, paying less than or equal to market-rate prices for its solar juice.

And those savings are coming at a time when energy costs are depressed due to the Meltdown and other factors. When utility costs rise - as most observes believe they will - Walmart will be sitting pretty. ®