A method for satisfying consumers’ demands for energy and transport services at the lowest societal and environmental cost. The method was first used for energy services, but least-cost planning can now be applied in various service sectors. For example, in transport systems, benefits include more balanced and efficient transportation, more cost-effective investments, more flexible solutions, and a more diverse transportation system. Least-Cost Planning is by definition more economically efficient than planning that restricts the range of solutions that can be applied to transportation problems. A more diverse and efficient transportation system tends to increase consumer savings and choice. A less automobile-dependent transportation system tends to reduce road risk and environmental costs.