A Wal-Mart store in in Oakland, Calif.
A Wal-Mart store in in Oakland, Calif. - 

Jeremy Hobson: Now to the world's biggest retailer, Wal-Mart. When the company does something -- even if its as small as which brand of lightbulbs it sells, changing that brand -- it has huge implications.

Well now, as Marketplace's Eve Troeh reports, Wal-mart is giving a solar energy company a boost.

Eve Troeh: Walmart sees renewable energy as a way to save money. Joel Makower at GreenBiz.com says long-term contracts for solar power insulate Walmart from roller coaster prices on the grid.

Joel Makower: They can lock in lower energy prices, they can predict their electricity costs years out from now.

Walmart's banking heavily on Solar City, a company that uses emerging technology in thin solar film instead of traditional solar panels. Next week, Solar City and Walmart will expand their partnership.

Lawrence Gasman at NanoMarkets says Walmart does take on risk by backing a newish technology, but it's a different kind of risk than government loans.

Lawrence Gasman: They make judgment calls based entirely on profit, whereas the government is trying to do some stuff which has to do with jobs, which is a much harder way to do investment.

Solar City just landed a big loan guarantee from the government -- $344 million -- as part of a deal to put solar power on military housing. Gasman says the solar industry now attracts enough private money that the government guarantees are not essential. But federal subsidies are crucial for growth.

I'm Eve Troeh for Marketplace.

Follow Eve Troeh at @evetroeh