Operational Emissions
In short: operational emissions come from the electricity a web application uses while it runs: on servers, on users' devices and, optionally, in the network between them. Each part is the energy used multiplied by the carbon intensity of the electricity grid that supplied it.
Shape: server emissions + device emissions (+ network emissions, if reported) = operational emissions.
Worked: 300 kg CO2eq (servers) + 150 kg CO2eq (devices) = 450 kg CO2eq for a month; adding 20 kg CO2eq of network emissions gives 470 kg for the second, labelled score. (illustrative placeholder, not a real measurement)
Precise notation:
O = O_server + O_client [+ O_network, optional]
O_x = E_x × I_x (E in kWh, I in gCO2eq/kWh, location-based)
The components
- Server-side emissions (
O_server): origin, application, database, storage, caching, edge and serverless infrastructure, up to the data centre's exit point to the network. - Client-side emissions (
O_client): rendering and running the application on end-user devices. - Network emissions (
O_network), optional: transmitting data from the data centre's exit point to the user's device.
Clause 5.1 makes O_server and O_client mandatory. Clause 5.2 makes
O_network optional, and Clause 7.1 requires the score without it always
to be reported. The Formula Walkthrough
explains why.
Location-based carbon intensity only
Clause 7.1 requires every operational component to use location-based carbon intensity, and Clause 11 excludes market-based measures. In practice that means the following never reduce an SCI for Web score:
- carbon offsets or credits;
- renewable energy certificates (RECs) and other energy attribute certificates (EACs);
- power purchase agreements used to claim carbon-neutral energy;
- "green hosting" claims based only on renewable energy purchases.
These may be worth reporting elsewhere, but not as a reduction in the score. Where to find location-based data is covered on Carbon Intensity and Data Sources.
Third-party services
Third-party operational emissions are not a separate component. They are
counted inside O_server, O_client or O_network, wherever the
service executes, and Clause 7.6 requires each reported operational
component to show first-party and third-party sub-totals. See
Third-Party Attribution.
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