  Many organizations, including governments, utilities, and businesses, have
set ambitious targets to reduce carbon emissions for their Environmental,
Social, and Governance (ESG) goals. To achieve these targets, these
organizations increasingly use power purchase agreements (PPAs) to obtain
renewable energy credits, which they use to compensate for the ``brown'' energy
consumed from the grid. However, the details of these PPAs are often private
and not shared with important stakeholders, such as grid operators and carbon
information services, who monitor and report the grid's carbon emissions. This
often results in incorrect carbon accounting, where the same renewable energy
production could be factored into grid carbon emission reports and separately
claimed by organizations that own PPAs. Such ``double counting'' of renewable
energy production could lead organizations with PPAs to understate their carbon
emissions and overstate their progress toward sustainability goals, and also
provide significant challenges to consumers using common carbon reduction
measures to decrease their carbon footprint. Unfortunately, there is no
consensus on accurately computing the grid's carbon intensity by properly
accounting for PPAs. The goal of our work is to shed quantitative and
qualitative light on the renewable energy attribution and the incorrect carbon
intensity estimation problems.
