In 2018 businesses, households and government enterprises throughout the global economy spent an estimated €7.4 trillion to meet the many demands for various energy services. Current projections suggest that the present scale of annual expenditures may increase by more than 60 percent to €12.0 trillion by 2050 (with all costs expressed in real 2018 values). Although the global economy derives important benefits from the purchase of many energy services, the inefficient use of energy also creates an array of costs and constraints that burden our social and economic wellbeing. Among these costs or constraints are increased health costs, air pollution, climate change and a less productive economy—especially over the long term. Yet there is good news within the countless energy markets throughout the global economy. Whether improved lighting in homes and schools, transporting people and goods more efficiently, or powering the many industrial processes within any given nation, there are huge opportunities to improve the productive use of energy in ways that reduce total economic costs. And those same energy efficiency upgrades can also reduce greenhouse gas emissions that drive climate change, as well as lessen other impacts on both people and the global environment. However, as this manuscript suggests, it will take an adequately funded set of smart policies and effective programs, including a skilled work force, to drive the optimal scale of energy efficiency investments.