718,803 MWh of untapped energy
“718,803 MWh of untapped energy”
wrong Retired in version 2.0.0, 2 October 2026.
Where it appeared: Home page: energy bars, ratio and map bubbles; Page description and social-card text (index.html); Social image (og-image.svg).
Why it failed
The number was 3,938,648 (the sum of Welsh Water's catchment 'population' layer, close to its 3.96 million population equivalent) × 0.5 kWh per person per day × 365. The 0.5 had no source. It is about the theoretical chemical energy in all wastewater, not what sludge can yield: Welsh Water's own tables imply about 0.03 kWh of electricity per resident per day. Welsh Water already generates 141.8 GWh a year from sludge, about a fifth of what we called 'untapped'.
Evidence
- Welsh Water, Annual Performance Report 2025-26, tables 8A, 8C, 8D
- Welsh Water, APR 2024-25 table 7D.16: population equivalent 3,959.6 thousand
- Heidrich et al. (2011), energy in domestic wastewater
- Annotated v1 model, with published and corrected values side by side
What the site says now
Energy generated from sludge (sourced), electricity per resident (sourced), and a rough ceiling (estimate with working) on /figures.