Thames Water used 532 kWh of net electricity for each megalitre of water it supplied in FY 2025/26, up 1.5% on the year and higher than the 525 kWh it used in FY 2019/20. Over the same six years, its total electricity use fell only modestly, from 1,305 GWh to 1,254.4 GWh.
Leakage carries an energy bill
Annual average leakage rose to 573.7 Ml/d in FY 2025/26, about 22% of the 2,568.31 Ml/d the company put into supply. At its average water intensity, that lost water represents roughly 111 GWh of electricity a year spent pumping and treating water that was never used. Leakage was 15.1% below the 2019/20 baseline on a three-year average, short of the 21.3% regulatory target.
Dry years add pumping
The company says the dry spring and wet winter of FY 2025/26 "increased electricity usage for pumping and treatment." It hired additional pumps during the drought, and water resources spending ran £34.5 million above its regulatory allowance. It gave the same explanation for missing its energy targets in FY 2019/20. A Temporary Use Ban has applied to all of its drinking water customers since July 23, 2026.
Wastewater moved the other way
Net electricity per megalitre of wastewater treated fell to 252 kWh, down 7.4% on the year and slightly below 254 kWh in FY 2019/20. Total energy use, which includes heat and fuels, still rose 18 GWh to 1,647 GWh, and combined heat and power outages pushed up grid imports.
How these energy pressures compare across Thames Water's supply options, what its sludge generation and power contracts can offset, and which energy investments it can fund without a net zero allowance are examined in the full report. The full report, Water-Energy Nexus: Thames Water, is available for USD 499 at https://ourfuturewaterintelligence.com/reports/water-energy-nexus-thames-water. For a free overview, read the Thames Water Utility Snapshot at https://ourfuturewaterintelligence.com/utilities/thames-water.