Investors have poured money into yieldcos over the past several years to get their hands on an income stream generated by renewable power. However, doing so has been a losing proposition, as leading yieldcos 8point3 Energy Partners (NASDAQ: CAFD), TerraForm Power (NASDAQ: TERP), NRG Energy Partners (NYSE: NYLD), and NextEra Energy Partners (NYSE: NEP) are down sharply over the past few years.