Residential customers in England and Wales cannot choose their water and wastewater company. Developers and other third parties must also receive certain services from one of the 17 largest water only and water and wastewater companies we regulate
We encourage the 17 companies providing these monopoly services to deliver better services by (among other things) using incentives. This includes:
- the Customer Measure of Experience (C-MeX), which measures the quality of services delivered to household customers
- the Developer Services Measure of Experience (D-MeX), which measures the quality of services to developers and other third parties
Each company is ranked for C-MeX and D-MeX and receive:
- a positive financial payment if they do better than expected (‘outperformance’)
- a negative financial payment if they do worse (‘underperformance’).
Below, we have published league tables which show how each company has performed during 2019-20.
This is a trial (or ‘shadow’) year so companies are ranked but do not get any payments. Companies will receive these payments from 2020-21 onwards.
2019-20 results
Customer Measure of Experience (C-MeX) 2019-10 results
Overall, Dŵr Cymru has topped the C-MeX league table during the shadow year with Portsmouth Water in second and Wessex Water in third place.
| Rank | Company | Shadow year C-MeX scores |
| 1 | Dŵr Cymru | 82.47 |
| 2 | Portsmouth Water | 82.09 |
| 3 | Wessex Water | 81.05 |
| 4 | United Utilities | 79.76 |
| 5 | Northumbrian Water | 79.64 |
| 6 | Yorkshire Water | 79.20 |
| 7 | Anglian Water | 79.01 |
| 8 | Bristol Water | 78.13 |
| 9 | Severn Trent Water | 77.65 |
| 10 | South Staffs Water | 77.47 |
| 11 | South West Water | 76.35 |
| 12 | Hafren Dyfrdwy | 75.01 |
| 13 | South East Water | 73.36 |
| 14 | SES Water | 72.85 |
| 15 | Affinity Water | 72.70 |
| 16 | Southern Water | 68.85 |
| 17 | Thames Water | 65.12 |
Developer Services Measure of Experience (D-MeX) 2019-10 results
Portsmouth Water tops the D-MeX league table with Wessex Water in second and Northumbrian Water in third place.
| Rank | Company | Shadow year D-MeX scores |
| 1 | Portsmouth Water | 87.81 |
| 2 | Wessex Water | 87.73 |
| 3 | Northumbrian Water | 86.62 |
| 4 | Severn Trent Water | 86.27 |
| 5 | Anglian Water | 85.91 |
| 6 | South West Water | 85.64 |
| 7 | United Utilities | 85.46 |
| 8 | Bristol Water | 84.92 |
| 9 | Dŵr Cymru | 84.38 |
| 10 | South East Water | 82.05 |
| 11 | South Staffs Water | 81.56 |
| 12 | Thames Water | 79.34 |
| 13 | Hafren Dyfrdwy | 78.73 |
| 14 | Southern Water | 75.70 |
| 15 | SES Water | 74.83 |
| 16 | Affinity Water | 74.38 |
| 17 | Yorkshire Water | 69.57 |
About C-MeX and D-MeX
We introduced the customer measure of experience (C-MeX) and developer services measure of experience (D-MeX) as part of the 2019 price review (PR19). Both mechanisms are designed to incentivise the 17 largest water companies to provide excellent levels of service to their customers.
C-MeX replaces the service incentive mechanism (SIM) as our key tool to drive companies to improve the experience of residential customers while D-MeX incentivises companies to provide an excellent experience for developer services customers, such as property developers requesting a new connection.
During 2019-20 (the ‘shadow year’) we piloted both mechanisms to help inform our final decisions for PR19. While financial incentives did not apply to C-MeX or D-MeX during the shadow year, these scores indicate how the sector is currently performing and sets the baseline for future years.
We publish league tables which show how each company has performed during the shadow year and an annual report produced by our survey agent BMG Research.
Now with both incentives in effect since 1 April 2020, companies stand to incur significant underperformance payments or outperformance payments based on how they score relative to each other every year – with the largest company facing returning up to £20m a year to its customers if it performs poorly. We are confident that C-MeX and D-MeX will encourage companies to strive to improve customer experiences while also measuring performance across companies consistently, reliably and fairly.
How C-MeX is measured
C-MeX is based on two surveys conducted each month with residential customers:
- the customer service survey (CSS) – based on interviews with a random sample of customers that have recently contacted their company, using a mixture of telephone and online surveys; and
- the customer experience survey (CES) – based on interviews with a random sample of members of the public, using a mixture of telephone and face-to-face surveys. 80% of each company’s C-MeX score is based on the customer satisfaction score and a further 20% on the net promoter score where customers are asked how likely they are to recommend their water company.
How D-MeX is measured
D-MeX has two components which measure the service provided by water companies to their developer services customers (which include large and small property developers, self-lay providers, new appointees and other customers requesting a new connection):
- a qualitative component – based on monthly interviews with developer services customers that have transacted with a water company in the previous month
- a quantitative component – based on the water company’s performance against a key set of Water UK metrics which measure the service provided by water companies to their developer services customers.
More information
More information on the methodology for C-MeX and D-MeX can be found here: