Customer and developer services experience

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

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

As part of PR19, we are introducing 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 has been in place since 2010.

They are both primarily survey based incentive mechanisms, measuring direct customer feedback. D-MeX also has a quantitative component, being 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.

We will finalise guidance for companies, the survey agent and relevant stakeholders by March 2020.


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.

Key documents

Final determinations

We confirmed our final policy decisions for C-MeX and D-MeX in our 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 also produced draft PR19 reconciliation models to demonstrate how company scores, outperformance and underperformance payments will be calculated each year. We will consult on and finalise these models in 2020.

Draft determinations

We set out draft decisions in our PR19 draft determinations in July 2019 – see annex 5 of ‘Delivering outcomes for customers policy appendix’. Companies and other stakeholders made representations on our draft determinations which we took into account as part of our assessment and final decisions.

Shadow year policy documents

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

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

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 here.