Exploring the cost implications of increased renewable energy for the U.S. power system

Abstract

Over the last decade, the fraction of annual U.S. electricity generation for renewable energy has doubled from 10 % to 20 %. This growth has been driven by several factors, including technology cost reductions and policy support. The share of renewable generation is projected to increase over time. Reference case scenarios from four different organizations show least-cost U.S. electricity buildouts with renewable energy generation fractions of 31–36 % by 2030 and 40–65 % by 2050. Using a capacity expansion modeling tool, we investigate how changing the amount of renewable energy from the least-cost solution impacts the cost of building and operating the electricity system. The relationship between system cost and renewable energy generation fraction is non-linear. Small deviations near the least-cost solution have minimal cost impacts (changing the renewable energy penetration by +/- 5% results in system cost changes of less than 1%), while similar deviations that are farther from the least-cost solution can result in large cost changes. Increased levels of RE lead to lower absolute emissions, and we evaluate the trade-offs between emissions savings and system costs for higher and lower levels of RE penetration.