Feasibility of U.S. renewable portfolio standards under cost caps and case study for Illinois

► RPSs mandate that generation by non-hydro renewables in the U.S. double by 2025. ► Implementation of many RPSs is impossible without decreases in renewable costs. ► The Illinois wind requirement can largely be met by existing Iowa windpower. ► Placing technology carveouts under one cost cap allows pernicious interactions. ► The Illinois RPS statute combines different objectives inherently in conflict.