But when these investments began to shrink, few investors went back in. Since 2009, VCs barely funded 25 new cleantech companies a year, slowing investment to a trickle. From 2011 to 2016, US venture capital investment in cleantech declined from 650 deals a year to 450 deals a year and from 17% of total venture capital dollars to 7%.Few VCs went to back the start-ups, because the sector itself could not deliver the outsized returns found in other sectors could deliver (i.e. software and even medical technologies) Commercializing cleantech would require a more diverse set of actors and funding models. The once-hot sector turned into a graveyard.