Nationalise water and large energy firms: note

Central fiscal result

+£30.0bn - Net fiscal impact in 2028-29

Low case: +£10.0bn. High case: +£80.0bn. Positive numbers are fiscal costs or borrowing pressure. Negative numbers are Exchequer savings or receipts.

Scenario and baseline

• Models nationalise water and large energy firms by 2028-29.
• Baseline is current policy or published departmental plans.
• Central case uses published party or official anchors where available.
• Wider manifesto interactions are excluded unless stated.

Affected population

• Affected units are people, firms, households or providers depending on policy.
• Direct exposure follows the manifesto or government target group.
• Indirect exposure includes suppliers, workers, consumers and taxpayers.
• Weakest counts are widened in the low and high cases.

Gross impact

• Published anchor or scenario central is +£30.0bn in 2028-29.
• Gross costs or receipts are adjusted for behaviour and delivery risk.
• Tax, benefit or procurement offsets are separated in the fiscal build-up.
• The range is deliberately wider where implementation detail is thin.

Fiscal build-up, central case

• Gross programme or delivery cost: +£34.5bn
• Tax and receipt offsets: -£2.4bn
• Administration and evaluation: +£0.1bn
• Behavioural and pass-through effects: -£2.2bn

Central net impact: +£30.0bn in 2028-29.

Behaviour and pass-through

• Low case assumes stronger delivery or receipts than central.
• Central case applies moderate behavioural leakage and pass-through.
• High case allows weaker delivery, larger take-up or higher costs.
• Output effects follow incidence, capacity and investment channels.
• Distributional gains do not automatically imply GDP gains.

Phasing

• 2026-27: +£3.0bn. Phased implementation and take-up.
• 2027-28: +£16.5bn. Phased implementation and take-up.
• 2028-29: +£30.0bn. Phased implementation and take-up.
• 2029-30: +£30.0bn. Phased implementation and take-up.

Main source groups

• Banerjee and Duflo, "Do Firms Want to Borrow More?" (Review of Economic Studies, 2014): Some firms are credit constrained, so public finance can support investment when well targeted; relevant to development banks and business finance.
• Institute for Fiscal Studies, "Green Party manifesto: a reaction" (2024): Used to define the pledge wording, policy scope and implementation scenario being modelled.
• Local Government Association, "Green Party manifesto summary" (2024): Used to define the pledge wording, policy scope and implementation scenario being modelled.
• Kotlikoff and Summers, "Tax Incidence" (Handbook of Public Economics, 1987): The legal payer of a tax is not necessarily the person bearing its economic burden; supports incidence discussion across taxes.
• Ofwat, "Monitoring financial resilience in the water sector" (2025): Ofwat reports financial-resilience pressures, high debt and investment needs across water companies; compensation and debt assumptions dominate the fiscal range.
• HM Treasury, "Spending Review 2025" (2025): Public investment baselines affect whether nationalisation sits on top of existing capital plans; used to frame public-balance-sheet risk.
• Green Party of England and Wales, "Manifesto for a Fairer, Greener Country" (2024): The manifesto defines the tax, spending, climate, housing and public-service proposals modelled here; used to define the scenario, not as an official costing.