Abstract
Provincial carbon footprint factors of electricity underpin product carbon footprints, green certificate trading, and carbon border adjustment, yet their uncertainty is usually reported as one aggregate interval that does not show which part better measurement could reduce and which part an accounting convention fixes. This case study examines eight plants in one Chinese province with original 2025 accounting workbooks (four coal-fired, four hydropower). Each is rebuilt into a normalized parametric model reproducing the original total. Measurable quantities are propagated by Monte Carlo sampling and apportioned with variance-based sensitivity indices; database choices and accounting conventions are enumerated as discrete scenarios and compared with, rather than added to, the probabilistic interval. For the coal-fired plants, the measurement-driven 95% interval is about −11% to +12%, dominated by coal input; the background database shifts the factor by a comparable amount, whereas every accounting convention shifts it by less than 30% of the interval half-width. For the hydropower plants, the interval is wider, yet harmonizing the amortization horizon of civil works alone moves the factor by 1.5 to 2.8 times that half-width. The findings are specific to the sample and suggest differentiating data collection and factor publication by generation type.