Guidance

1. Introduction to EPA methodology

Updated 16 June 2026

Applies to England and Wales

• Publication for Northern Ireland
• Publication for Scotland

We, the Environment Agency and Natural Resources Wales, introduced the Environmental Performance Assessment (EPA) in 2011. It is a non-statutory tool for comparing performance between the 10 largest water and sewerage companies operating in England and Wales. They are:

• Anglian Water Services Limited
• Dŵr Cymru (Welsh Water)
• Northumbrian Water Limited
• Severn Trent Water Limited
• Southern Water Services Limited
• South West Water Limited
• Thames Water Utilities Limited
• United Utilities Water Limited
• Wessex Water Services Limited
• Yorkshire Water Services Limited

The EPA uses measurable environmental metrics to provide a meaningful comparison of their performance. Water and sewerage company performance for each EPA metric is given a red, amber or green (RAG) status. Based on performance across all the metrics, EPA numeric ratings are then applied to each company. More information on RAG thresholds for EPA metrics is in section 3, and on ratings including a core metric approach is in section 4.

The EPA for the 9 water and sewerage companies operating wholly or mainly in England is published by the Environment Agency on GOV.UK. It forms part of a report, produced annually, on the ‘environmental performance of the water and sewerage companies’. Additional summary and supporting information is published with the main report including an EPA metric guide and company specific data reports. Natural Resources Wales publishes an ‘annual performance report for Dŵr Cymru (Welsh Water)’ containing their EPA. More information on our reporting of 2026 to 2030 data is in section 6.

This methodology provides technical information on how we complete the EPA and which water and sewerage company performance data from our regulation is included. The target audience is water and sewerage companies and interested stakeholders and the public.

There are some differences in how the EPA is completed between the Environment Agency and Natural Resources Wales. These are explained in relevant sections of this methodology and summarised in section 5. Natural Resources Wales also publishes an annual report on the environmental performance of Hafren Dyfrdwy. However, it does not apply this EPA methodology in full due to the small size of the company.

1.1 EPA review for 2026 to 2030 data

Every 5 years we review the EPA to focus attention on how water and sewerage companies are meeting statutory obligations and our performance expectations. Our reviews broadly align with the 5 year asset management plan (AMP) investment cycles for water and sewerage companies to make improvements and meet our expectations. The AMP periods are linked to price reviews (PR) carried out by the economic regulator Ofwat – PR19 for 2020 to 2025 (AMP7) and PR24 for 2025 to 2030 (AMP8).

Between 2 October 2024 and 2 December 2024, we jointly consulted stakeholders on our proposals to expand and strengthen the EPA for the 2026 to 2030 data years. The RAG thresholds we proposed were developed taking into account past performance and expectations. Expectations, including many with relevance to the EPA, were set out in the Water Industry Strategic Environmental Requirements (WISER) in England for 2026 to 2030. This was written by the Environment Agency and Natural England and released in May 2022. It applies to water and sewerage companies operating mainly in England. While WISER does not apply in Wales, a Welsh Water Industry Strategic Environmental Requirements (WWISER) will be published in 2026. This will apply to water and sewerage companies operating in Wales or using Welsh water resources.

We have produced a consultation conclusions summary that explains what we heard from consultees, the decisions we reached and how we reached them.

Following the EPA review including the stakeholder consultation, we have set the EPA metric definitions and RAG status thresholds for 2026 to 2030 data. Green status means that metric performance is on track with the relevant WISER expectations. Amber status means some improvement is required and red status that significant improvement is required to meet relevant WISER expectations. Numeric ratings reflect performance across all EPA metrics. Water and sewerage companies are expected to be rated a 4 consistently. They will exceed expectations if they achieve the new 5th rating when live (2028 data year onwards), which requires green status for all EPA metrics.

The metric definitions are presented in section 2 of this methodology. Section 3 summarises the RAG status thresholds, and section 4 sets out the method for applying ratings.

1.2 Timescale and methodology updates

The metric definitions set out in section 2 include their ‘frequency of assessment’. Some metrics assess calendar year data and some assess financial year data. For example, where we assess and report 2026 data, we mean 1 January 2026 to 31 December 2026 for calendar year metrics and 1 April 2026 to 31 March 2027 for financial year metrics.

This EPA methodology version C for 2026 to 2030 data reporting applies for assessment of 2026 data onwards (from 1 January 2026 to 31 March 2031). This includes the publication of the 2026 data EPA in 2027. This version C replaces version B published and shared with companies in March 2026 and has:

• updated sections 1 (Introduction to EPA methodology), 2 (Definitions of the live EPA metrics) and 6.1 (Annual report publication) to include reference to Natural Resources Wales’ assessment and reporting of Hafren Dyfrdwy’s environmental performance
• updated section 1 to include WWISER
• updated section 1.5 (Governance of data and information submitted by companies) to clarify what we mean by board approval
• updated metric definitions in sections 2.1, 2.3, 2.4, 2.5, 2.6, 2.7 and 2.8 to include rounding method
• updated section 2.2 (Serious incidents affecting water) to update wording of expectation for zero serious incidents by 2030 in line with WISER
• updated section 2.4 (Discharge permit compliance) to clarify definition of ultraviolet (UV) samples
• updated section 2.9 for the water environment and security of supply delivery metric – this metric only applies to the 9 water and sewerage companies operating wholly or mainly in England
• added section 2.10 for the Supply Demand Balance Index (SDBI) metric which applies to Natural Resources Wales’ assessment of Dŵr Cymru (Welsh Water) and Hafren Dyfrdwy only
• updated table 3 (RAG thresholds for live EPA metrics) in section 3 to include the SDBI metric for Natural Resources Wales’ assessment of Dŵr Cymru (Welsh Water) and Hafren Dyfrdwy
• updated section 5 to set out that the water environment and security of supply delivery metric applies to the Environment Agency and water and sewerage companies in England only – the SDBI metric applies to Natural Resources Wales, Dŵr Cymru (Welsh Water) and Hafren Dyfrdwy only
• added appendix 2 – summary of changes to EPA methodology version A (for 2026 to 2030 EPA period) made in version B

At the time of this methodology publication, version 13 of the EPA methodology for the 2021 to 2025 period (released December 2025) applies for assessment of 2025 data to be published in 2026.

1.3 Shadow reporting

We carry out shadow (not published) assessments and reporting before new or changed EPA metrics become live (published). This allows us to:

• demonstrate new metrics or assessment approaches and see how they are working before they are fully in use
• amend metric definitions and refine data processes to ensure they are robust and timely
• provide information to focus companies on performance improvements
• inform our performance reviews with water and sewerage companies

Shadow assessments are ongoing for some metrics that are still being developed with the intention of becoming live in the period 2026 to 2030. These are:

• abstraction and impounding licence compliance (Environment Agency only)
• waste water treatment works (WWTW) flow to full treatment (FFT) annual numeric permit limit compliance

Definitions for these shadow metrics are included in section 7. We are also developing further EPA metrics for 2031 data onwards. We intend to carry out shadow assessments as these metrics develop during the period 2026 to 2030. More details on these metrics and our EPA forward look are in section 8. This includes WWTW dry weather flow (DWF) compliance – this metric definition is developed but requires WWTW to have had the required permit condition in place for sufficient time to enable a 4 year ‘look-back’ period (see section 8.3).

We will update the EPA methodology before a shadow metric becomes part of the live EPA.

1.4 Future EPA methodology revisions

We will update and republish the EPA methodology in advance of major changes. For example, before any amendments to metric definitions or before a shadow metric becomes part of the live EPA. This will include any amendments following the outcomes of any separate metric stakeholder consultations.

1.5 Overview of data and information processes

Data collection and assessment processes

This methodology provides technical information on how we complete the EPA and which water and sewerage company performance data from our regulation is included.

Governance of data and information submitted by companies

We expect all data and information that water and sewerage companies are required to formally submit to us for the EPA to have their board’s sign-off. We do not specify the exact process for this board approval. However, it means that companies must have board approved processes in place for collating, assuring and submitting accurate data. This includes taking steps during the year to ensure tracking procedures facilitate final board approval of the data and information submitted.

Local enforcement positions, regulatory position statements and regulatory decisions

Any permit or licence breach or pollution incident under a local enforcement position or regulatory position statement will be included in EPA reporting, unless otherwise agreed with the Environment Agency. Natural Resources Wales uses regulatory decisions where it recognises that some regulatory requirements are disproportionate to the risks to the environment and human health. For the sludge metric (section 2.7) sludge stored, used or disposed under a regulatory position statement in England will be recorded as satisfactory. However, sludge stored, used or disposed under a local enforcement position should be recorded as unsatisfactory sludge. Natural Resources Wales classes sludge stored, used or disposed of in compliance with the conditions of a regulatory decision as satisfactory.

Next: 2. Definitions of the live EPA metrics.