Customer and developer services experience

The customer and developer services measures of experience: C-MeX and D-MeX

Customer service was one of the four key themes of our 2019 price review (PR19). Providing an excellent customer experience for customers is fundamental for maintaining trust and confidence in the water sector.

As part of PR19, we introduced the customer measure of experience (C-MeX) and developer services measure of experience (D-MeX) which apply to the 17 largest water companies in England and Wales for the 2020-25 period.

C-MeX and D-MeX are financial and reputational incentive mechanisms designed to provide customers in the water sector with excellent levels of service. In effect from 1 April 2020, they replace the service incentive mechanism (SIM) which had been in place since 2010.

C-MeX and D-MeX are both primarily survey based incentive mechanisms, measuring direct customer feedback. D-MeX also has a quantitative component, being a measure of compliance against a set of Water UK developer services level of service metrics.

Companies receive a score based on the satisfaction ratings given by customers in monthly surveys (and additionally for D-MeX, company performance against key performance metrics). We will publish annual league tables for both C-MeX and D-MeX, showing each company’s score. Each company can receive outperformance payments or incur underperformance payments based on how it scores compared to other companies.


The customer measure of experience (C-MeX) is designed to incentivise water companies to provide an excellent customer experience for residential customers, across both the retail and wholesale parts of the value chain.

C-MeX comprises two surveys – the customer service survey of residential customers who have recently contacted their company in relation to that recent contact and the customer experience survey of random members of the public in relation to their experience of their water company.

In both cases customers are asked how satisfied they are with the service provided and how likely they would be likely to recommend the water company to family or friends. This net promoter score result is measured and reported separately to the C-MeX score which is used to calculate financial incentives.


The developer services measure of experience is designed to incentivise water companies to provide an excellent customer experience to developer services customers, including small and large property developers, self-lay providers and those with new appointments and variations (NAVs). These customers can also include residential customers that have new mains connections installed.

D-MeX comprises a qualitative element which is a survey of developer services customers who have recently completed a transaction with their water company and a quantitative element which measures performance against a set of Water UK developer services level of service metrics.

A full list of the metric definitions used for D-MeX is available.

Key documents

In-period consultations (2020-25)

On 30 September 2020 we published a decision document on changing the developer services measure of experience (D-MeX). The document sets out our decision on adding new metrics developed by Water UK that relate to the services provided to NAVs and the adoption of sewerage assets. These changes took effect from 1 October 2020.

More information is available on changes to performance commitments in the 2020-25 period.

Guidance for the 2020-25 period

In March 2020 we published the final guidance for how C-MeX and D-MeX will operate during the 2020-25 period. These documents are designed to help water companies ensure they are able to provide the necessary information for the successful operation of C-MeX and D-MeX, and to support the survey agent as they conduct the C-MeX and D-MeX surveys on our behalf.

Shadow year reporting guidelines

On 2 April 2020 we published guidelines on how water companies should calculate and report their shadow year C-MeX and D-MeX scores and proxy scores for the service incentive mechanism (SIM) in their 2019-20 annual performance reports.

PR19 reconciliation

We produced draft spreadsheet models for C-MeX and D-MeX as part of our consultation on the PR19 reconciliation rulebook in March 2020. These models demonstrate how company scores, outperformance and underperformance payments will be calculated each year during the 2020-25 period.

We will finalise these spreadsheet models in 2020.

PR19 final determinations

We confirmed our final policy decisions for C-MeX and D-MeX in the PR19 final determinations, published in December 2019 – see ‘Customer measure of experience (C-MeX) and developer services measure of experience (D-MeX) policy appendix’. As part of PR19, the 17 largest water companies have common performance commitments for C-MeX and D-MeX, which are set out in each company’s outcomes performance commitment appendix.

We took into account stakeholders’ representations on our PR19 draft determinations (see annex 5 of ‘Delivering outcomes for customers policy appendix’) as part of our assessment and final decisions.

Any changes to performance commitments in the period 2020-25 are available.

We have published full definitions of common and some comparable performance commitments.

Shadow year policy documents

C-MeX and D-MeX operated in shadow form from 1 May 2019 to 31 March 2020. In March 2019 we set out the policy decisions and guidance that would apply for the shadow year:

Our decisions were supported by recommendations from the survey agent we appointed to pilot these incentives in 2018-19 (read more information about the pilot year study) and stakeholder views from the C-MeX and D-MeX working groups and sub-groups (read more information about our stakeholder engagement).

Related information

Data protection

We appointed a survey agent to carry out the interviews for C-MeX and D-MeX on our behalf.

If you are a residential or developer customer, find out more information about our approach to data protection for these surveys.