Power games: The invention and reporting of electricity grid emission factors

The electricity we consume derives from many different sources – power generators with different characteristics, including widely divergent greenhouse gas emissions per unit of output, which vary both geographically and temporally. The integrated nature of electricity grids means that it is physically impossible to differentiate between electrons according to how or where they were generated. Nevertheless, characteristics such as the greenhouse gas emissions of electricity supply at a given place and time can be measured. Converting these measurable characteristics of electricity supply into reportable characteristics for electricity consumption poses various challenges, however. These challenges are compounded when an entity wishes to account for avoided electricity supply resulting from low-­‐carbon electricity generation, energy efficiency or demand reduction. This paper examines what these challenges are and how they have been dealt with in various carbon accounting frameworks. Principally, this has involved the invention of a new metric to convert units of energy generated or saved into units of carbon dioxide or carbon dioxide equivalent: the grid emissions factor. What the grid emission factor means and how it should be calculated is shown to be contested, and more complicated than this apparently simple concept might first suggest. In particular, the paper focuses on the debate around the use of ‘contractual’ or market-­based versus ‘locational’ electricity grid emission factors. The issuance of new guidance on this matter by the Carbon Disclosure Project (CDP) and World Resources Institute/World Business Council for Sustainable Development Greenhouse Gas Protocol raises important questions about the politics of ‘private’ regulation of carbon accounting and disclosure.