C-MeX and D-MeX 2022-23 Results
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’).
Performance commitments are the pledges companies made to their customers and stakeholders at the 2019 price review (PR19) about service levels to make progress towards their outcomes. Where a company outperforms against its performance commitments, it sees relevant increases in the amount of revenue it can recover in its price controls. Where a company underperforms against its performance commitments, this reduces the amount of revenue companies can recover from customers.
The financial payments associated with C-MeX and D-MeX will be detailed in the companies in period draft determinations and these outperformance and underperformance payments will be confirmed as final at final determination stage of the in period process.
Customer Measure of Experience (C-MeX) 2022-23 results
| Rank | Company | C-Mex score | Payment (£m) |
| 1 | Northumbrian Water | 83.74 | 3.368 |
| 2 | Portsmouth Water | 83.17 | 0.243 |
| 3 | Wessex Water | 82.99 | 1.610 |
| 4 | Welsh Water | 82.92 | 2.191 |
| 5 | United Utilities | 81.26 | 3.024 |
| 6 | Bristol Water | 80.68 | 0.214 |
| 7 | Hafren Dyfrdwy | 80.03 | 0.032 |
| 8 | South Staffs Water | 79.87 | 0.127 |
| 9 | Severn Trent Water | 79.08 | 0.000 |
| 10 | Anglian Water | 78.77 | -0.262 |
| 11 | Yorkshire Water | 78.25 | -0.510 |
| 12 | South West Water | 76.45 | -0.697 |
| 13 | SES Water | 76.03 | -0.138 |
| 14 | Affinity Water | 74.59 | -1.060 |
| 15 | South East Water | 73.47 | -0.937 |
| 16 | Southern Water | 69.77 | -3.657 |
| 17 | Thames Water | 67.06 | -13.121 |
Developer Services Measure of Experience (D-MeX) 2022-23 results
| Rank | Company | D-Mex score | Payment (£m) |
| 1 | Hafren Dyfrdwy | 92.88 | 0.046 |
| 2 | Portsmouth Water | 91.96 | 0.085 |
| 3 | Severn Trent Water | 91.4 | 2.669 |
| 4 | Bristol Water | 89.99 | 0.139 |
| 5 | Wessex Water | 89.89 | 0.237 |
| 6 | Northumbrian Water | 89.85 | 0.452 |
| 7 | South Staffs Water | 87.57 | 0.044 |
| 8 | United Utilities | 87.43 | 0.046 |
| 9 | Anglian Water | 87.27 | 0.000 |
| 10 | Affinity Water | 86.36 | -0.202 |
| 11 | South West Water | 86.02 | -0.308 |
| 12 | SES Water | 84.91 | -0.105 |
| 13 | Welsh Water | 84.68 | -1.127 |
| 14 | South East Water | 82.74 | -0.748 |
| 15 | Southern Water | 80.56 | -1.817 |
| 16 | Thames Water | 80.46 | -5.320 |
| 17 | Yorkshire Water | 80.08 | -2.857 |
About C-MeX and D-MeX
We publish league tables each year which show how each company has performed during the year and an annual report produced by our survey agent Accent.
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.
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.