What is carbon accounting?
Carbon accounting is measuring and reporting the greenhouse gas emissions an organisation causes, usually as a CO2e inventory split into three scopes.
Why it matters
A carbon inventory multiplies activity data, such as kWh of electricity, by an emission factor to estimate emissions in CO2e. The GHG Protocol Corporate Standard sets out how to draw boundaries, sort emissions into Scope 1, 2 and 3, and report them so inventories are consistent and transparent.
Cloud is one of the harder areas to account for. The servers and data centres belong to the provider, so the customer has a bill to work from and no meter to read. Spend-based estimates turn that bill into emissions with average factors. They are hard to check in an audit and miss the effect of changing an instance type or region.
An example
A team moves a workload to a different instance type in the same region and the monthly bill stays about the same. A spend-based estimate shows no change. A usage-based calculation picks up the different hardware, its electricity and its embodied emissions, so the effect of the change shows up in the carbon figure.
How Greenpixie measures it
Greenpixie calculates cloud emissions from usage data and uses no cost or spend information. For each line of a cloud bill it works through four steps:
- map the service, region, period and quantity to the hardware behind it and estimate IT electricity
- add data centre overhead using the region's PUE
- multiply by the grid carbon intensity for that region and hour
- add the line's share of embodied hardware emissions
The results are added to the billing data as new columns, and every original column is kept. Emissions can then be grouped by the same accounts and services as cost.