This article offers a literature review on the system of certificates for attributing sources of decarbonized electricity generation, with a particular focus on how temporal matching rules between certificate consumption and production affect their consequential performance in reducing emissions. First, we explain how the electricity attribution certificates (EAC) system operates, describing its annual functioning and carbon accounting implications. Second, we identify how consumption’s motivations for attribution under the annual system led to new decarbonization ambitions justified by a switch to hourly matching practices. Also driven by the 24/7 Carbon-Free Electricity (CFE) procurement initiative, which combines temporal, regional, and additionality matching criteria, a growing body of literature has established a consequential modeling framework for the power system of each potential matching system. Drawing from this targeted corpus, we compare the effects of annual, hourly, and 24/7 CFE initiatives in terms of emissions reductions, transformation of the electricity mix, and induced costs. On the one hand, we note that the literature converges on the limited ability of annual matching to generate structural system impacts and additional emissions reductions. On the other hand, literature models significant environmental benefits from the 24/7 CFE procurement initiative, which more strongly directs investment toward decarbonized technologies available during residual hours of variable renewable generation, thereby reducing reliance on fossil fuels. However, we find that none of the studies isolate the effect of a standalone hourly-matching reform. Moreover, we highlight the limitations of the modeled results, including modeling assumptions, additional induced costs, and alignment with the attribution market architecture. This work illustrates a trade-off between a low-cost annual mechanism and a costly new market for 24/7 CFE procurement, contributing to the ongoing discussion on potential reform of the GHG Protocol.
