Thames Water sustainability score: 36/100
Making progress starts at 46. The highest score on SINK is 71.
Thames Water Utilities Limited supplies water and sewerage services to London and the Thames Valley. It was formed on privatisation in 1989 and is headquartered in Reading.
More about Thames Water
Its filed accounts for the year to 31 March 2026 report revenue of £3,756.5m, including £140.9m passed through for the Thames Tideway Tunnel, and an average of 8,472 permanent employees. It is regulated by Ofwat and the Environment Agency.
Founded 1989Head office Reading, United KingdomStaff ~8,472Revenue £3,756.5M (FY2025/26, year to 31 March 2026)Website ↗
The Environment Agency rated Thames Water 1 star ('poor performing company') for 2024, and in 2025 Ofwat imposed a record £122.7m penalty. In 2025/26 it had 24 serious pollution incidents, discharge permit compliance of 88.22% and average leakage of 573.7 Ml/d. No third-party assurance of its greenhouse gas figures was found. Its zero market-based Scope 2 relies on supplier renewable electricity, and its reported Scope 3 covers operational categories only, with no capital carbon.
Thames Water scores 36/100 (Below expectations) on SINK's independent climate assessment, scored from public data only. Scores are free. Nobody can pay to change a score, speed it up or hide it. Last verified October 2026.
That places Thames Water joint 542nd of 1,023 companies scored, and 11th of 11 in Water & Sewerage.
What is Thames Water doing well, and where does it fall short?
Strongest on Carbon Footprint: Operations and Energy Source (6/10, 6/10). Weakest on Water Impact and Controversies & Red Flags (1/10, 2/10).
Where Thames Water lost points
For each question that lost points, the evidence our public rubric looks for that we didn't find.
What would raise this score
- Its effect on waterPublish figures for its water use.
- Its record on controversiesDeal with the findings under question 10, in public.
- Whether its emissions are fallingShow its emissions are falling.
Every question that lost points
- Emissions from its own operations6/10Its own emissions aren't independently verified or tracked over several years.
- Emissions from its supply chain4/10Most of its supply-chain (Scope 3) emissions aren't measured.
- Whether its emissions are falling3/10No evidence its emissions are falling.
- How clean its energy is6/10Less than 90% of its energy shown to be renewable.
- Its effect on nature3/10No assessment of its effect on nature, and no basic environmental policy.
- How it uses materials and handles waste4/10No measurable waste or recycling targets reported publicly.
- Its effect on water1/10No figures for its water use.
- Its climate targets3/10No specific targets with dates.
- How openly it reports5/10No dedicated sustainability role, board oversight or public report.
- Its record on controversies2/10Points deducted for controversies or its business model. The finding is under question 10.
A score changes when the evidence does. We use new published evidence at the next rescore. Anyone can send us new evidence, free. How to send it.
How is Thames Water's SINK score calculated?
Same ten questions for every company. No private weighting.
SINK = (0.3 × Base + 0.7 × Performance) × ScaleWhat evidence is Thames Water's score based on?
9 sources used in this assessment. All publicly available. Each row shows which of the ten questions it informed.
33% of them were published by Thames Water itself; the rest come from independent sources.
“In 2025/26 the water sector, in agreement with industry regulator Ofwat, has adopted an updated emissions factor for nitrous oxide”
“Includes fossil fuels, site process and fugitive emissions and vehicle transport (Fleet).”
“In 2024/25 we self-generated and used 475.3GWh of renewable energy, covering 25.8% of our own energy needs.”
“RWE will supply a total of 132 gigawatt hours (GWh) of clean electricity annually”
“33 serious incidents – this is rated as red”
“Thames Water has been fined £122.7 million after two investigations into wastewater and dividend payments, in the largest penalty Ofwat has ever issued”
If you believe a source has been misread or a newer version exists, submit a challenge.
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How does Thames Water compare with other water & sewerage companies?
Thames Water sits at the bottom of the water & sewerage pack.
Among the 11 major water & sewerage brands we've scored, Thames Water sits 11th of 11.
Who scores higher in Water & Sewerage?
The 3 companies in the sector scoring nearest above Thames Water.
Yorkshire Water's market-based emissions rose from 281 to 295 ktCO2e between FY2024 and FY2025, and Scope 1 rose from 85 to 88 kt.
See the breakdown →Southern Water's gross Scope 1 and 2 emissions were flat between 2022–23 and 2024–25 (152,364 t to 152,320 t, location-based), and its Scope 3 rose about 35% year on year.
See the breakdown →Dŵr Cymru Welsh Water's total market-based emissions rose 9% to 443.4 kt in 2025/26, and its emissions targets are under review.
See the breakdown →Which companies moved this week, and why.
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