In 2025-26, Thames Water's supply plan for London counted on 97 Ml/d of water from hosepipe bans and non-essential use restrictions in a dry year. After bans in 2022 and 2025, the company now says its data suggest "it will be difficult to achieve the levels of demand savings currently estimated."
Heat drives the peaks
Smart meter readings from 2025 show where the pressure comes from. During the summer's heatwaves, household use rose 23% to 30% in terraced, semi-detached and detached homes with gardens. The 2025 ban covered only the Swindon and Oxfordshire zone, ran from July 22 to November 27, 2025, and came into force after three of the four heatwaves.
The 2026 test
This year the ban is company-wide. It took effect on July 23, 2026, when customers were using about 100 million liters a day more than normal. Since then, demand has fallen by up to 3% in London and up to 6% in the Thames Valley and Home Counties. On October 12, 2026, the ban remained in place.
The Thames area has been in drought since July 29, 2026. On September 16, London's reservoirs held 59% against an average of 78%, and the Environment Agency granted a drought permit at Farmoor on September 29.
What changes next
Thames Water now plans for bans once in ten years on average, up from once in 20. Its draft 2027 Drought Plan aims to bring bans in faster, and its next water resources plan will revise the savings it counts on. Lower assumed savings mean a larger gap for leakage reduction and new supply to fill before White Horse Reservoir is due in 2040.
The report examines how each supply zone moved against plan, the schemes due before 2030 and the milestones regulators will decide in the next year. The full report, Climate Resilient Water Resources Management: Thames Water, is available for USD 499 at https://ourfuturewaterintelligence.com/reports/climate-resilient-water-resources-management-thames-water. For a free overview, read the Thames Water Utility Snapshot at https://ourfuturewaterintelligence.com/utilities/thames-water.