C-MeX and D-MeX - 2019-20 results

Below, we have published league tables which show how each company has performed during 2019-20.

This was a trial (or ‘shadow’) year so companies are ranked but did not get any payments. Companies are receiving these payments from 2020-21 onwards.

2019-20 results

Customer Measure of Experience (C-MeX) 2019-20 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) 2019-20 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.

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.

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: