The U.S. today relies on 100 nuclear power plants for roughly 20% of its electricity. Were it not for a wave of plant cancellations starting in the mid-1970s — prompted, in part, by the financing costs of the era, but exacerbated by the overreaction to the Three Mile Island accident — U.S. nuclear capacity could have significantly increased; in fact, U.S. nuclear capacity might plausibly be double what it now is.