Every five years the economic regulator for England and Wales, Ofwat, decides how much each water company may spend, what it may charge and what it must deliver. AMP8, the eighth such period, runs from 1 April 2025 to 31 March 2030 and was fixed by the PR24 final determinations in December 2024. For an engineer, the determination is not a finance document: it is the origin of every performance target, environmental scheme and capital programme that will land on their desk this decade. This guide explains the mechanism and the commitments.
How a price review works
Companies submit business plans setting out proposed expenditure and outcomes; Ofwat challenges them against its own efficiency models, cost benchmarks and the requirements of the environmental regulators, then publishes draft and final determinations. For each company the determination sets:
- Total expenditure (totex) allowances: operating and capital spending combined, split into base (maintaining service) and enhancement (improving it) with the enhancement element tied to named outputs.
- Revenue and bills: the allowed revenue path and hence the bill trajectory, indexed to inflation.
- Performance commitments (PCs): numeric service levels, common across companies for the main measures, with outcome delivery incentives (ODIs) that pay or penalise per unit of over- or under-performance.
- Price control deliverables (PCDs): specific enhancement outputs (a named storm tank, a phosphorus removal scheme) with money clawed back if they are late or undelivered.
A company that disagrees can ask for a redetermination by the Competition and Markets Authority, and several did after PR24. Engineers should therefore check their own company's final position, since figures can move after the Ofwat determination.
The scale of AMP8
Ofwat's December 2024 final determinations allowed total expenditure of roughly £104 billion across England and Wales for 2025-2030, about double the previous period in real terms, with average bills rising by around a third over the five years before inflation. Three themes dominate the enhancement programme:
- Storm overflows: of the order of £12 billion to reduce spills, with a stated ambition to cut the number of spills by roughly 45 percent against the 2021 baseline over the period, as the first instalment of the Storm Overflows Discharge Reduction Plan targets to 2050.
- Water resources and resilience: new reservoirs, transfers and reuse schemes, with leakage reductions of about 17 percent across the period on the path to the 50 percent reduction by 2050 against the 2017-18 baseline.
- Nutrients and the environment programme: phosphorus removal, sanitary determinands and habitat schemes under the Water Industry National Environment Programme (WINEP) in England and the National Environment Programme in Wales.
These are headline figures; each company's allowances, PCs and PCDs are set out in its own determination documents and should be read directly for any scheme-level work.
Performance commitments that drive engineering
Common performance commitments in AMP8 are where regulation becomes measurable engineering. Those that matter most for process and network engineers:
| Commitment | Unit | Engineering levers |
|---|---|---|
| Storm overflow spills | Average spills per overflow per year (EDM data) | Storm storage, infiltration reduction, surface water separation, SuDS, increased flow to full treatment |
| Leakage | Ml/d, three-year average | Pressure management, active leakage control, mains renewal, smart metering |
| Internal and external sewer flooding | Incidents per 10,000 connections | Capacity, blockage prevention, pumping station resilience |
| Pollution incidents | Incidents per 10,000 km of sewer | Pumping station monitoring, rising main condition, overflow screening |
| Mains repairs and unplanned outages | Repairs per 1,000 km; minutes lost per property | Renewal targeting, pressure management, resilience of supply |
| Discharge permit compliance | Percent of works compliant | Process capacity, nutrient removal, monitoring and control |
| Water quality (CRI) and customer contacts about appearance and taste | Index; contacts per 1,000 population | Treatment, mains flushing and cleaning, lining |
Because ODIs are priced per unit, a company can calculate the value of a spill avoided or a megalitre of leakage saved, and that value feeds into the economic case for schemes. Engineers designing pressure management or storm overflow reduction will find the ODI rate is the number that decides whether a marginal scheme proceeds.
WINEP and the environment programme
WINEP is the Environment Agency's list of actions each company must take to meet environmental obligations: permit tightening at named works, investigations, flow monitoring, habitat and catchment schemes. It is the source of most process-engineering enhancement work: a phosphorus permit tightened to 0.25 mg/L creates a tertiary dosing or filtration project; a new flow-to-full-treatment condition creates a hydraulic and storm storage project; a sanitary determinand change creates a secondary treatment upgrade.
Each WINEP line has a driver code, a delivery date and, in AMP8, a strong emphasis on verifiable outputs. For design, the practical consequences are a fixed completion date (often with regulatory dates mid-period), a defined permit limit the process must meet including under winter and peak-load conditions, and the MCERTS flow monitoring needed to prove compliance. Permit compliance itself is covered in the water quality and compliance hub.
The wider regulatory changes around AMP8
AMP8 began amid the most significant regulatory reform since privatisation. The Water (Special Measures) Act 2025 strengthened enforcement powers, made executives personally accountable for certain failures and required monitoring of all emergency overflows. The Independent Water Commission, reporting in 2025, recommended structural reform of regulation, including replacing Ofwat with a single integrated regulator, and the government has indicated it will legislate. Engineers should expect reporting requirements to increase during the period, particularly on overflow monitoring, flow measurement and asset health, rather than wait for PR29.
For contractors and consultants, the practical effect is that AMP8 frameworks were let on larger, longer programmes with a strong preference for standard product solutions, off-site build and early contractor involvement. Programme scale also exposes the industry's skills constraint: the same determination that doubles the capital programme does not double the number of chartered process engineers, which is why specialist process design capacity and packaged, pre-tested plant have become central to delivery.
What an engineer should take from the determination
- Find the PCD for your scheme. It states the output, the date and the money; late delivery is clawed back, so the programme is a contractual obligation, not an aspiration.
- Design to the performance commitment, not the permit alone. A storm tank that meets its permit but does not reduce spill count enough to move the company's average does not deliver the ODI value that justified it.
- Build in the monitoring. Every PC is measured; EDM on overflows, MCERTS flow at works, DMA metering for leakage. A scheme without its measurement is unverifiable and, in regulatory terms, undelivered.
- Read the base and enhancement split. Maintaining an asset is base totex; improving its performance is enhancement. Classifying work correctly matters for how it is funded and reported.
- Expect the targets to tighten. AMP8 targets are a step on the path to 2050 obligations on spills, leakage and nutrients; a design with no headroom will be back on the programme in AMP9.
Frequently asked questions
What are the AMP8 dates?
AMP8 runs from 1 April 2025 to 31 March 2030. Ofwat's PR24 final determinations, published on 19 December 2024, set the period, with some companies subsequently seeking redetermination by the Competition and Markets Authority.
What is the difference between a performance commitment and a price control deliverable?
A performance commitment is a service level measured across the company, such as leakage in megalitres per day or spills per overflow, with financial incentives per unit of over- or under-performance. A price control deliverable is a specific named output, such as a particular storm tank or treatment upgrade, with funding clawed back if it is not delivered on time.
What is WINEP?
The Water Industry National Environment Programme is the Environment Agency's schedule of environmental actions each water company in England must deliver in the period, from permit tightening at named works to investigations and catchment schemes. It is the main source of process-engineering enhancement projects. Wales has an equivalent National Environment Programme set by Natural Resources Wales.
How do storm overflow targets in AMP8 relate to the 2050 targets?
The Storm Overflows Discharge Reduction Plan sets targets for 2035, 2045 and 2050, including limiting overflows to an average of no more than ten spills a year by 2050 and prioritising high-priority sites earlier. AMP8 funds the first instalment, reducing spills substantially against the 2021 baseline, with the rest programmed into later periods.