Temporal matching as an accounting principle for green electricity claims

Labeling electricity as green typically relies on annual volumetric matching of certificates. Recent studies have shown that hourly matching can improve the environmental effectiveness of green electricity procurement. Responding to the European Union's push for more transparent and reliable green products, we assess how stricter temporal matching affects green electricity claims. Using data from the European certificate and electricity market, we analyze quarterly, monthly, weekly, daily, and hourly matching. We find substantial seasonal and intra-day mismatches between green electricity supply and demand that remain hidden under annual matching. As certificates already allow monthly granularity, we propose a two-phase transition: short-term adoption of quarterly or monthly matching to reduce seasonal accounting distortions, followed by hourly matching to address increasing day-night disparities. Fully integrating storage systems into certificate schemes is crucial for this transition. Our findings inform current policy debates, such as the revision of the Greenhouse Gas Protocol Scope 2 Guidance.