Energy-resource diversity is key to decreasing the chances of energy system failure, preserving system reliability in the face of increasingly extreme weather events and increasing public support for aggressive climate action. Overreliance on any single energy source, technology or delivery system often leads to unintended consequences in the future and diminishes public support for meaningful climate action. Finding the right mix of energy solutions for a city, state, or utility system requires consideration of a full range of strategies in various mixes that address every sector, deploy all emissions reduction options and are flexible enough to allow for shifts to rapidly emerging technologies. Pre-selecting ‘winning’ technologies or making decisions to shut down energy sources that residents and businesses across all sectors currently rely on will reduce the role that innovation can play in supporting emissions reductions and make it more difficult and expensive to achieve our climate goals.