Emissions and cost tradeoffs of time-matched clean electricity procurement under inter-annual weather variability: case study of hydrogen production

Abstract: Time-matching requirements (TMRs) for clean electricity procurement are increasingly adopted in voluntary corporate sustainability initiatives and regulatory frameworks. While prior research has evaluated cost and emissions impacts of hourly vs. annual TMR, these studies typically rely on single-year weather scenarios that do not capture inter-annual variability in variable renewable energy (VRE) generation. We use a capacity expansion model to assess how inter-annual weather variability affects procurement-driven infrastructure investments, costs, and emissions for a grid-connected hydrogen producer under both annual and hourly time-matching strategies. Using a Texas case study, we compare deterministic (single weather scenario) and stochastic (nine weather scenarios) modeling approaches. Both procurement investments and cost and emissions outcomes are sensitive to weather scenario, with annual matching exhibiting greater sensitivity than hourly matching. Stochastic modeling finds higher cost premiums for hourly versus annual matching compared to deterministic modeling, though emissions trends remain directionally consistent. Demand flexibility through H2 storage is critical for lowering hourly matching cost premiums under weather-driven VRE variability. Partial hourly matching (e.g., 80-90% compliance) can modestly reduce costs while maintaining minimal emissions impacts. Finally, we examine how grid-level renewable portfolio standards (RPS) affect additionality and emissions. When stringent additionality is achieved via binding RPS constraints on non-H2 electricity demand, annual matching can produce emissions reductions comparable to hourly matching at lower cost.