In two decades of experience with state renewable portfolio standards (RPSs), the United States has observed immense growth in renewable energy markets, initially in wind energy and more recently in solar power. During this time, RPSs have experienced considerable policy reinvention and increased diversity. Here, we explain how changes in RPS policy design features relate to different market outcomes. We develop a score for measuring RPS stringency and show that a one-point increase in RPS stringency leads to increases of 0.2%, 1% and 0.3% in renewable energy, solar generation and renewable energy capacity, respectively. Other important design features include resource eligibility, planning processes, cost recovery and geographical restrictions. These findings are then reaffirmed through 42 semi-structured phone interviews with experts in the field of RPS implementation from government agencies, including public utility commissions and state energy offices, electric utilities and various renewable energy firms and associations.
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The code used to generate the statistical results in the present study, applicable to STATA 14, is available from the corresponding author upon request.
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We acknowledge research assistance provided by J. Amadon, D. Baldwin, C. Davis, V. Luman, M. McKay, N. Mitchell, D. Olson, J. Williams, M. Williams and R. Woolston. Library research support was provided by S. Darais, R. McPhail and F. Murphy.
The authors declare no competing interests.
This research involved human subjects. It was approved with exempt status by the University of Utah, under protocol number 00063847. In accordance with this protocol, informed consent was provided by all study participants
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Carley, S., Davies, L.L., Spence, D.B. et al. Empirical evaluation of the stringency and design of renewable portfolio standards. Nat Energy 3, 754–763 (2018). https://doi.org/10.1038/s41560-018-0202-4
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