  This paper presents a methodology for allocating energy consumption to
multiple users of shared data center machines, infrastructure, and software.
Google uses this methodology to provide carbon reporting data for enterprise
customers of multiple Google products, including Google Cloud and Workspace.
The approach documented here advances the state-of-the-art of large scale Cloud
carbon reporting systems. It uses detailed, granular measurement data on
machine energy consumption. In addition, it uses physical factors for
allocating energy consumption and carbon emissions--preferred by the Greenhouse
Gas Protocol's Scope 3 Reporting Standard. Specifically, the approach described
here allocates machine energy consumption based on a combination of data center
resource reservations and hourly measured resource usage. It also accounts for
Google's own internal use of shared software services, reallocating energy use
to the users of those shared services. Finally, it uses hourly,
location-specific estimates of carbon intensity to precisely measure carbon
emissions of users in a global fleet of data centers.
