A number of US states have passed renewable portfolio standard, a mandate that ensures a certain amount of energy to be generated by renewable sources, to offset carbon emission or create local jobs. While states\u27 renewable portfolio standards have similar features, their designs vary substantially. In this paper, I investigate the design features and renewable energy certificate prices in five northeastern states that are trading in two trading systems to see how renewable portfolio standards are working in those states. The regression on bidding and asking price differences reveals considerable differences among states in Class I renewable energy certificate prices and differences between bid and asking price. This leads us to question the effectiveness of these portfolio standards
