Ask "how much CO₂e does a kilowatt-hour of electricity cause?" and there is no single correct answer. Unlike a fuel with a physical carbon content, grid electricity's emissions depend on how the power was generated — which changes with place and time.
Three things the answer depends on
- Region. A kWh from a hydro- or nuclear-heavy grid carries a fraction of the emissions of a kWh from a coal-heavy grid. There is no global factor.
- Year. Grids decarbonise (or occasionally re-carbonise) over time, so last decade's factor is not this year's.
- Time of day. Even within a region and year, the mix shifts hour to hour as demand and renewable output change.
Because of this, a single "electricity → CO₂e" number with no context would be confidently wrong for almost everyone.
What the tool does: context required
With no region and year supplied, converting kWh electricity to CO₂e returns context required — not a number, and not "unsupported". The result:
- explains that grid carbon intensity depends on region, year and even time of day;
- surfaces a region + year picker so you can pin down the context;
- where illustrative factors exist in the data, shows one or more clearly-labeled example outputs — each tagged as an illustrative example, not a default, with its region, year and source, visually separated from computed results.
Once you supply a region and year and a cited factor exists, the tool returns a normal region- and year-specific value carrying that label and its source.
No default country factors in v0.1
Deliberately, v0.1 ships no authoritative country-by-year grid factors as defaults. Baking in a single national number would invite exactly the false-precision error the tool exists to avoid; per-country presets are on the roadmap for later versions. For the deeper distinction between the metrics involved here, see CO₂ vs CO₂e.