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.
This is the first year of that companies will receive financial payments and these have been detailed in the companies in period draft determinations. 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) 2020-21 results
| Rank | Company | C-Mex score | Payment (£m) |
| 1 | Portsmouth Water | 86.22 | 0.283 |
| 2 | Wessex Water | 86.09 | 2.022 |
| 3 | Northumbrian Water | 85.76 | 2.927 |
| 4 | Welsh Water | 85.15 | 2.014 |
| 5 | United Utilities | 83.59 | 2.076 |
| 6 | Bristol Water | 83.31 | 0.162 |
| 7 | Anglian Water | 83.05 | 1.127 |
| 8 | Yorkshire Water | 82.78 | 0.466 |
| 9 | Severn Trent Water | 82.35 | 0 |
| 10 | South Staffs Water | 81.89 | -0.080 |
| 11 | Hafren Dyfrdwy | 81.38 | -0.035 |
| 12 | South West Water | 80.96 | -0.536 |
| 13 | South East Water | 80.70 | -0.401 |
| 14 | SES Water | 78.97 | -0.226 |
| 15 | Affinity Water | 77.88 | -1.545 |
| 16 | Southern Water | 74.64 | -4.906 |
| 17 | Thames Water | 72.92 | -16.753 |
Developer Services Measure of Experience (D-MeX) 2020-21 results
| Rank | Company | D-Mex score | Payment (£m) |
| 1 | Severn Trent Water | 89.70 | 3.881 |
| 2 | Wessex Water | 89.47 | 0.698 |
| 3 | Portsmouth Water | 89.20 | 0.099 |
| 4 | Hafren Dyfrdwy | 89.01 | 0.035 |
| 5 | United Utilities | 88.44 | 1.053 |
| 6 | Anglian Water | 87.72 | 1.175 |
| 7 | Northumbrian Water | 86.94 | 0.354 |
| 8 | Bristol Water | 86.81 | 0.055 |
| 9 | South West Water | 85.88 | 0 |
| 10 | Affinity Water | 84.39 | -0.094 |
| 11 | South Staffs Water | 83.59 | -0.073 |
| 12 | Dŵr Cymru | 82.69 | -0.354 |
| 13 | South East Water | 79.85 | -0.239 |
| 14 | Thames Water | 77.56 | -1.861 |
| 15 | Southern Water | 73.77 | -1.033 |
| 16 | Yorkshire Water | 62.25 | -2.884 |
| 17 | SES Water | 60.20 | -0.344 |
Supporting documents
Accent report: C-MeX and D-MeX 2020-21
About C-MeX and D-MeX
Following the shadow year of 2019-20 where we piloted the mechanisms, we have now completed the first year of surveying for C-MeX and D-MeX reporting. While financial incentives did not apply to C-MeX or D-MeX during the shadow year, they now do and these have been detailed in the Companies in period draft determinations. We have not made direct comparisons to the shadow year due to some methodological differences, however this now gives us the benchmark that we will be comparing performance against looking forward.
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.
Now with both incentives in effect since 1 April 2020, companies are incurring significant underperformance payments or outperformance payments based on how they score relative to each other every year – with the largest return of £17.9m a year (C-MeX) to its customers for poor performance. This demonstrates that C-MeX and D-MeX encourages 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.
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.
* Following the introduction of new self-lay water metrics by Water UK, in February 2021 we consulted on changing the metrics for self-lay providers in D-MeX. In March 2021, we published our assessment and final decisions.
We also consulted on changing the metrics relating to the services provided to NAVs and the adoption of sewerage assets, providing an opportunity for stakeholders to comment in July 2020 and September 2020 we published our assessment and final decisions
Page updated 22 November 2021