“100% renewable” electricity contracts: Assessing availability and emissions through temporal analysis

Electricity contracts marketed as "100% renewable" are typically based on certification schemes like Guarantees of Origin, which certify production sources but fail to ensure linkage between generation and consumption. This study evaluates the availability and emission impact of temporally and geographically matched green electricity contracts using granular data on renewable generation, cross-border transmission flows, emission factors, and household electricity consumption. Results reveal major discrepancies between Guarantee of Origin-based claims and actual renewable availability. Solar-only contracts are infeasible for continuous supply, while wind-only contracts could meet just 0.03%–0.11% of Finland's total hourly load continuously in 2021–2023. Households could still achieve substantial emission reductions with the proposed temporally and geographically matched renewable contracts, but 100% savings cannot be guaranteed due to limited availability and competing demand for renewables. Solar contracts could offer up to 41% annual emission savings, though savings decline rapidly as solar demand exceeds availability. Household heating type has little effect on percentage savings, while electric-heated homes with mixed-renewable contracts achieve the highest absolute savings. Load shifting presents a viable alternative, offering average theoretical emission savings of 8%–10% with a 12-hour shifting window, demonstrating significant emission reduction opportunities without requiring specific green contracts. • Evaluation of temporally and geographically matched green electricity contracts. • Exclusively solar or wind power contracts are infeasible for year-round supply. • Household emission savings depend on renewable availability and external demand. • Load shifting enables realistic emission savings without specific green contracts.