"Solar has plunged by 90% in cost. Wind has plunged by 80% just in the past 11 or 12 years. . . . Things like wind and solar power really can already out-compete dirtier forms of electricity, and we just need to build more of them quickly; we’re not adding them fast enough. There are other technologies where we really need a big breakthrough. We don’t yet have affordable enough heat pumps. We don’t yet have a next generation nuclear technology that’s cheap enough, if we ever will. Geothermal is really at the cusp of becoming something that I think could really take off. What I also see, though, is that what carries those cutting-edge technologies to the cheaper cost can’t just happen in the lab. We need policies that pull those into the market, that get them adopted more — because if we can adopt them while they’re at that edge; while they’re not quite cheap enough, that can drive the economies of scale; that can drive what technologists call learning by doing."