Planning for a Sustainable Future with an Electric Utility: Emissions Reductions and Cumulative Carbon Budgets

Project Dates

TEP contracted with CLIMAS, based on a previous research partnership, to explore plausible scenarios for greenhouse gas and carbon reduction in their energy portfolio. These scenarios focus on data internal to TEP regarding the economics of portfolio decisions and external social, environmental, or climatic factors that might affect these decisions. CLIMAS provided a critical assessment of the overall process to ensure that robust data and models were used in this scenario development. The project analyzed energy portfolios based on emissions reduction targets and cumulative carbon budgets. These results identify whether the portfolio will hit specified warming targets (e.g., 1.5°C, 2°C) based on the carbon emissions. They also suggest expected temperature increases for each portfolio. Results from this project will inform the company’s 2020 integrated resource plan.

Cumulative emissions offer a robust and empirical method to assess the warming impact of utility energy portfolio scenarios. They assess both the timing and intensity of emissions reductions, and highlight the additional emissions reductions that result when reductions move more quickly than a straight linear reduction. This emphasizes that the way these targets are achieved may be just as important as the targets themselves.

The TEP Carbon Goals – Data and Process GitHub Repository — contains the data and analysis University of Arizona researchers used to guide Tucson Electric Power's carbon goals as part of their 2020 IRP process. The models, assumptions, code, documentation, and results are publicly available. The code is open source and fully transparent. Anyone can replicate, test, or improve our analysis, or update it based on new information or data. The repository was cited in a news story, published on TEP’s 2020 IRP web page, and cited in their 2020 IRP. Members of TEP’s Stakeholder Advisory Council have given comments, responded to ideas, and provided suggestions for the repository.