Not all options are ready to step into the spotlight, though. Master limited partnerships (MLP) and real estate investment trusts (REIT) promise more attractive tax treatment than securitizations or yieldcos, but they require some heavy lifting and difficult decisions at the highest levels: MLPs need an act of Congress even for an infinitesimal language tweak to remove a legislative exclusion to solar and wind, while REITs involve a touchy reclassification of assets from the IRS that could have broader and undesirable tax consequences. Yet another model gaining traction is a more institutionalized version of crowdfunding, led by Mosaic (technically they call it "crowdsourcing"), but crowdfunding is awaiting more clarity from the Securities and Exchange Commission about what rules must apply.