In the last five years, Google has poured more than $700 million into financing for clean energy projects. That’s not the kind of thing you do just to burnish your “green” credentials for a credulous public — it’s serious money, deployed with the express aim of diversifying the company’s holdings with “businesses that can earn good returns and that aren’t correlated to other investments,” says Rick Needham, Google’s director of green business operations.

Google’s success at making real money on its green investments suggests to Marc Gunther of Greenbiz that every tech company with gigantic cash holdings — i.e. Apple and Microsoft — should be parking at least some of them in targeted clean energy investments.

In fact, there are tons of projects out there in need of financing. Banks continue to chase phantom returns in other, less material instruments, so it’s time that the companies in the U.S. that actually make things step up, argues Gunther.

Google is filling an important financial gap. Other companies could, too. Apple recently reported eye-popping earnings which left it with $97 billion cash and short-term investments (although much of it is parked overseas). GE has $78 billion. Toyota has $48 billion. Microsoft has $43 billion.

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