"A number of studies have zeroed in on the influence of voluntary RECs—those purchased by private customers—on renewable energy production and have gathered significant evidence to suggest that these certificates have had little to no impact. One of these studies, led by researchers at Princeton, Harvard, and UCLA, for example, found that if the power market for voluntary RECs did not exist, “the amount of electricity generated by wind power in the United States would be little different than what we actually see today.”
A paper published in 2022 in Nature which received significant attention from the media argued that due to the drop in the prices of RECs in recent years, the revenue associated with these certificates is insufficient to promote an increase in green energy production. The paper concludes that while the group of companies being analyzed reported a combined 30.7% reduction in emissions resulting from their REC purchases, the actual reduction was closer to 9.9%."
https://kleinmanenergy.upenn.edu/commentary/blog/renewable-e...