Which UK water company has the best performance in 2024-25?

SES Water scores highest on the Gera Water Service Score (GWSS) at 93.2/100 in 2024-25. This reflects the lowest leakage in England and Wales (68 litres per property per day) plus a Compliance Risk Index of 0, the lowest recorded. Data from Ofwat Annual Performance Report 2024-25 and DWI, via DiscoverWater.co.uk.

What is the Gera Water Service Score (GWSS)?

GWSS is a Gera-computed composite index (0–100) for UK water companies, combining three independently published open datasets: leakage per property per day (Ofwat APR, weight 40%), average supply interruptions per property in minutes (Ofwat APR, weight 30%), and Compliance Risk Index/CRI from the Drinking Water Inspectorate (weight 30%). All three metrics are inverted so that lower values = higher scores. Higher GWSS = better performance.

Which water company leaks the least water?

In 2024-25, Essex and Suffolk Water and Bristol Water tied for the lowest leakage at 64 litres per property per day — well below the England and Wales average of 109 l/p/d. Dŵr Cymru Welsh Water had the highest leakage at 169 l/p/d. Source: Ofwat APR 2024-25, via DiscoverWater.co.uk.

Which water company has the fewest supply interruptions?

Portsmouth Water had the fewest supply interruptions in 2024-25, averaging just 00:02:01 of lost supply per property. The England and Wales average was 22 mins per property. Southern Water and Dŵr Cymru Welsh Water had the highest interruptions (over 2 hours per property). Source: Ofwat APR 2024-25.

What is the Compliance Risk Index (CRI)?

The CRI (Compliance Risk Index) measures each water company's overall performance against national drinking water quality standards. It is published annually by the Drinking Water Inspectorate (DWI). A CRI of 0 means all tests passed. A higher CRI indicates more quality compliance failures. The England and Wales average in 2024 was 3.72. Source: DWI, via DiscoverWater.co.uk.

Can I switch my water company in the UK?

For household customers in England and Wales, water supply is determined by your location — you cannot choose your household water provider. However, you can compare your company's performance using the GWSS and similar tools, and hold your company accountable via Ofwat, the Consumer Council for Water (CCW), and your company's own complaints process.

GeraMarket / UK water company performance

UK Water Company Performance Rankings

Real Ofwat APR 2024-25 data on leakage, supply interruptions, and DWI water quality (CRI) for all 19 UK water companies — ranked by the Gera Water Service Score (GWSS/100).

Which UK water company performs best?

As of Ofwat APR 2024-25 / DWI 2024, SES Water ranks highest of all 19 UK water companies on the Gera Water Service Score (GWSS), scoring 93.2/100 — driven by low leakage (68 l/p/d), minimal supply interruptions (00:26:40), and a near-zero Compliance Risk Index (0) per Ofwat APR and DWI data (OGL v3.0).

Source:Ofwat Annual Performance Report 2024-25 + DWI CRI 2024 (via DiscoverWater)·as of Ofwat APR 2024-25 / DWI 2024updated annually (last: 20 June 2026)

Gera Water Service Score93.2 / 100Top company: SES Water — Ofwat APR 2024-25 / DWI 2024How this index is calculated

Reference period: Ofwat APR 2024-25 / DWI 2024· Ofwat APR 2024-25 + DWI CRI 2024 · Open Government Licence v3.0 · England & Wales

Avg leakage

109 l/p/d

England & Wales 2024-25

Avg interruptions

22 mins

per property 2024-25

Avg CRI

3.72

DWI 2024

Median GWSS

70.8/100

across 19 companies

Top 10 water companies by GWSS (Ofwat APR 2024-25 / DWI 2024)

Top 10 UK water companies by Gera Water Service Score — Ofwat APR 2024-25 + DWI CRI 2024
Rank	Company	GWSS	Grade	Leakage	Supply interruptions	CRI
#1	SES Water	93.2/100	A	68 l/p/d	00:26:40	0.00
#2	Bristol Water	89.7/100	A	68 l/p/d	00:06:49	2.84
#3	Portsmouth Water	88.9/100	A	90 l/p/d	00:02:01	0.45
#4	Anglian Water	87.1/100	A	80 l/p/d	00:06:51	2.11
#5	Affinity Water	84/100	B	95 l/p/d	00:03:21	1.44
#6	South West Water	79.5/100	B	102 l/p/d	00:14:44	1.19
#7	Wessex Water	77.9/100	B	108 l/p/d	00:10:00	1.31
#8	South East Water	75.8/100	B	96 l/p/d	00:44:06	1.09
#9	Cambridge Water	73.1/100	B	80 l/p/d	00:15:04	6.58
#10	Yorkshire Water	70.8/100	B	111 l/p/d	00:08:27	3.61

All 19 water companies — full ranking

Rank	Company	GWSS	Leakage	Interruptions	CRI	Grade
#1	SES WaterSouth East	93.2/100	68 l/p/d	00:26:40	0.00	A — Excellent
#2	Bristol WaterSouth West	89.7/100	68 l/p/d	00:06:49	2.84	A — Excellent
#3	Portsmouth WaterSouth East	88.9/100	90 l/p/d	00:02:01	0.45	A — Excellent
#4	Anglian WaterEast of England	87.1/100	80 l/p/d	00:06:51	2.11	A — Excellent
#5	Affinity WaterSouth East	84/100	95 l/p/d	00:03:21	1.44	B — Good
#6	South West WaterSouth West	79.5/100	102 l/p/d	00:14:44	1.19	B — Good
#7	Wessex WaterSouth West	77.9/100	108 l/p/d	00:10:00	1.31	B — Good
#8	South East WaterSouth East	75.8/100	96 l/p/d	00:44:06	1.09	B — Good
#9	Cambridge WaterEast of England	73.1/100	80 l/p/d	00:15:04	6.58	B — Good
#10	Yorkshire WaterYorkshire	70.8/100	111 l/p/d	00:08:27	3.61	B — Good
#11	Essex and Suffolk WaterEast of England	69.4/100	64 l/p/d	00:04:40	10.94	C — Average
#12	South Staffs WaterMidlands	64.3/100	103 l/p/d	00:15:04	6.58	C — Average
#13	Hafren DyfrdwyWales	64.2/100	145 l/p/d	00:11:11	1.10	C — Average
#14	Thames WaterLondon & South	62.7/100	143 l/p/d	00:09:35	2.04	C — Average
#15	Severn Trent WaterMidlands	58.2/100	98 l/p/d	00:04:34	10.32	C — Average
#16	Northumbrian WaterNorth East	58/100	94 l/p/d	00:04:40	10.94	C — Average
#17	Southern WaterSouth East	50/100	89 l/p/d	02:21:50	3.82	D — Below average
#18	United UtilitiesNorth West	48.2/100	119 l/p/d	00:14:17	10.28	D — Below average
#19	Dŵr Cymru Welsh WaterWales	19.4/100	169 l/p/d	02:17:44	4.18	E — Poor

Compare water companies on any metric

Filter by region, sort by leakage, interruptions, or CRI, and see personalised GWSS breakdowns.

Filter by region

Sort by

Overall GWSS (highest first)

Company	GWSS	Leakage	Interruptions	CRI	Grade
#1SES Water	93.2/100	68 l/p/d	00:26:40	0.00	A
#2Bristol Water	89.7/100	68 l/p/d	00:06:49	2.84	A
#3Portsmouth Water	88.9/100	90 l/p/d	00:02:01	0.45	A
#4Anglian Water	87.1/100	80 l/p/d	00:06:51	2.11	A
#5Affinity Water	84/100	95 l/p/d	00:03:21	1.44	B
#6South West Water	79.5/100	102 l/p/d	00:14:44	1.19	B
#7Wessex Water	77.9/100	108 l/p/d	00:10:00	1.31	B
#8South East Water	75.8/100	96 l/p/d	00:44:06	1.09	B
#9Cambridge Water	73.1/100	80 l/p/d	00:15:04	6.58	B
#10Yorkshire Water	70.8/100	111 l/p/d	00:08:27	3.61	B
#11Essex and Suffolk Water	69.4/100	64 l/p/d	00:04:40	10.94	C
#12South Staffs Water	64.3/100	103 l/p/d	00:15:04	6.58	C
#13Hafren Dyfrdwy	64.2/100	145 l/p/d	00:11:11	1.10	C
#14Thames Water	62.7/100	143 l/p/d	00:09:35	2.04	C
#15Severn Trent Water	58.2/100	98 l/p/d	00:04:34	10.32	C
#16Northumbrian Water	58/100	94 l/p/d	00:04:40	10.94	C
#17Southern Water	50/100	89 l/p/d	02:21:50	3.82	D
#18United Utilities	48.2/100	119 l/p/d	00:14:17	10.28	D
#19Dŵr Cymru Welsh Water	19.4/100	169 l/p/d	02:17:44	4.18	E

Showing 19 of 19 UK water companies. Source: Ofwat APR 2024-25 + DWI CRI 2024, via DiscoverWater.co.uk (OGL v3.0).

Get water company performance alerts

Enter your email to receive the annual GWSS update when Ofwat publishes new APR data, plus water company news for your area.

Get notified View methodology

Frequently asked questions

Which UK water company has the best performance in 2024-25?: SES Water scores highest on the Gera Water Service Score (GWSS) at 93.2/100 in 2024-25. This reflects the lowest leakage in England and Wales (68 litres per property per day) plus a Compliance Risk Index of 0, the lowest recorded. Data from Ofwat Annual Performance Report 2024-25 and DWI, via DiscoverWater.co.uk.
What is the Gera Water Service Score (GWSS)?: GWSS is a Gera-computed composite index (0–100) for UK water companies, combining three independently published open datasets: leakage per property per day (Ofwat APR, weight 40%), average supply interruptions per property in minutes (Ofwat APR, weight 30%), and Compliance Risk Index/CRI from the Drinking Water Inspectorate (weight 30%). All three metrics are inverted so that lower values = higher scores. Higher GWSS = better performance.
Which water company leaks the least water?: In 2024-25, Essex and Suffolk Water and Bristol Water tied for the lowest leakage at 64 litres per property per day — well below the England and Wales average of 109 l/p/d. Dŵr Cymru Welsh Water had the highest leakage at 169 l/p/d. Source: Ofwat APR 2024-25, via DiscoverWater.co.uk.
Which water company has the fewest supply interruptions?: Portsmouth Water had the fewest supply interruptions in 2024-25, averaging just 00:02:01 of lost supply per property. The England and Wales average was 22 mins per property. Southern Water and Dŵr Cymru Welsh Water had the highest interruptions (over 2 hours per property). Source: Ofwat APR 2024-25.
What is the Compliance Risk Index (CRI)?: The CRI (Compliance Risk Index) measures each water company's overall performance against national drinking water quality standards. It is published annually by the Drinking Water Inspectorate (DWI). A CRI of 0 means all tests passed. A higher CRI indicates more quality compliance failures. The England and Wales average in 2024 was 3.72. Source: DWI, via DiscoverWater.co.uk.
Can I switch my water company in the UK?: For household customers in England and Wales, water supply is determined by your location — you cannot choose your household water provider. However, you can compare your company's performance using the GWSS and similar tools, and hold your company accountable via Ofwat, the Consumer Council for Water (CCW), and your company's own complaints process.

Compare by individual metric

Leakage rankings

Litres per property per day

Supply interruptions

Minutes lost per property

Water quality (CRI)

Compliance Risk Index

Contains public sector information published by Ofwat / Drinking Water Inspectorate and licensed under the Open Government Licence v3.0. Source: Ofwat Annual Performance Report 2024-25 + DWI CRI 2024 (via DiscoverWater) (Ofwat APR 2024-25 / DWI 2024, published June 2026 (APR 2024-25)).