The U.S. unlike Europe has state-wide targets that can be implemented on a voluntary or compliance basis. These renewable portfolio standards (RPS) also differ from European target counting in the fact that is largely based on in-state consumption not in-state production as is the case in Europe. This small change in how targets are counted allows the U.S. to have significantly higher RPS goals (for example 50% RES by 2030 in California) at much lower prices than in Europe. LBNL estimates that the total RPS compliance costs totaled 2.6 billion USD in 2014 averaging $12/MWh-RE or 1.3% of average retail electricity bills.

For more information on the LBNL report follow the link here.