Paid for by the public: as electricity billpayers, and as taxpayers standing behind the loans.
This page sets the published figures for Scottish offshore wind beside those for large nuclear power stations. Each figure carries a label saying where it comes from and the price year it is in. A cell that reads “not published” is blank because no figure was found. It has not been filled with an assumption.
Labels used: official = a government, regulator or audit-body document; filed = a company's own filed accounts; press = a company release or trade press; computed = exact arithmetic on published figures; estimate = this site's arithmetic or an assumption, shown; indicative = not yet final. No figure has been re-based to another price year unless it is marked estimateLabels on the evidence register showing how strong a figure's source is: an official document, a press report, arithmetic, or an estimate. more › and the arithmetic is shown.
BillpayersAnyone who pays an electricity bill. Most of the costs on this site are recovered this way, not from taxes. more › across the UK have paid at least £97bn for renewables so far, of which about £16bn went to Scottish renewables (the bill, the real cost). Hinkley Point C's whole cost is £35–36bn in 2015 prices for 3.2GW. Sizewell C's baseline is £38.2bn in 2024-25 prices.
Price bases, plainly: the £97bn is computed from three official series, two in the money of the day and one in 2024 prices (2023-24 prices in the NAO's figure note); the £16bn is an estimate. The Hinkley figure is official, from a National Audit Office (NAO) table of EDF's latest scenarios, February 2026, in 2015 prices. The Sizewell figure is official, the NAO's report of 20 May 2026, in 2024-25 prices. The £97bn is money paid so far, and it includes about £9.1bn for managing the grid bottleneck. The nuclear figures are costs to build. They measure different things, and this page does not subtract one from the other.
One row per question. Torness, an older station, appears where the question is about operating record, capacity, working life, ownership or decommissioningThe legal duty to remove offshore energy infrastructure and restore the site once it stops being used, paid for by the operator. more ›. Where no figure was found the cell says so.
| Item | Scottish offshore wind | Large nuclear: Hinkley Point C (HPC), Sizewell C (SZC); Torness for operating record |
|---|---|---|
| Cost to build |
£13.7–16.1bn for the ten Scottish-water farms built, including their offshore transmission assets. Nominal money spent 2007–2026, price years mixed. filed, press, estimate With Inch Cape, under construction: £17.2–19.7bn. filed, press, estimate Low and high are the lowest and highest whole-project figures found, not a forecast. |
HPC: £35–36bn, 2015 prices (EDF's latest cost scenarios, as printed by the NAO, February 2026). official HPC in 2024-25 prices: about £49.0bn. estimate The NAO says SZC's baseline is 22% lower than the lowest current HPC estimateLabels on the evidence register showing how strong a figure's source is: an official document, a press report, arithmetic, or an estimate. more ›; 38.2 ÷ (1 − 0.22) = 48.97. Inferred, not stated in one line. SZC: £38.2bn baseline, 2024-25 prices. official (NAO, May 2026). DESNZThe UK government department responsible for energy policy, including subsidy auctions and community fund guidance. more ›'s headline is “around £38 billion (2024 prices)”. official Whether the cost figures include interest during construction is not known; EDF's 2019 figure excluded it. |
| Capacity |
4,300.8 MWUnits of electrical power (MW) and energy (MWh, GWh): power is a rate, energy is power delivered over time. more › operating at the end of 2025. official, DESNZ Inch Cape, 1,080 MW, under construction. press, filed |
HPC: 3.2 GW (2 × 1.6 GW). official, NAO SZC: 3,278 MW planning capacity. official, DESNZ Torness: 1,200 MW. official, DUKES 2026 |
| Share of the time running |
23.5% in 2025, Scottish offshore wind. official, DESNZ regional table This is 8,870.24 GWh ÷ (4,300.775 MW × 8,760 h). computed UK offshore wind: 36.1% in 2025. official, DUKES 6.3 Caveat. The Scottish figure divides by year-end capacity, so a farm that came online part-way through the year counts at full size for the whole year. Neart na Gaoithe, for example, reports all 54 turbines commissioned and fully generating in May 2025 (filed). DESNZ's workbooks do not say why Scotland is below the UK figure; switch-off (curtailmentMoney paid to a generator to switch off, or reduce output, because the grid cannot carry all the power it is producing. more ›) and commissioning are possibilities, not findings. DESNZ also allocates offshore wind to a country by where the cable comes ashore. |
Torness: 82% in 2025 (8.6 TWh). press, EDF's own figure 75.6% in 2024 and 68.5% in 2022. estimate (EDF output ÷ DUKES capacity) UK nuclear fleet: from 56.82% (2021) to 72.85% (2018) across 2018–2025; 64.04% in 2025. official, DUKES 5.10.B EDF attributes the lower 2025 output to an extended outage at Hartlepool. press Sizewell B: 99% in 2025. press, EDF HPC and SZC are not yet operating. DESNZ models SZC at 90%: an assumption, not an outcome. official |
| Guaranteed price per MWh |
Moray East: £82.34, indexedA price or allowance that rises each year in line with inflation, so its real value stays roughly constant. more ›, 22 Sep 2026 (base strikeThe fixed price per unit of electricity that a wind farm is guaranteed under its subsidy contract. more › £57.50, 2012 prices). Beatrice: £205.70, indexed, 22 Sep 2026 (strike £140, 2012 prices). Both contracts are two-way: billpayersAnyone who pays an electricity bill. Most of the costs on this site are recovered this way, not from taxes. more › pay, or receive, the difference from the market price. official, LCCC data, as shown on risk.html Latest auction, Scottish fixedLabels on the evidence register showing whether a figure's source was checked and confirmed, corrected, missing, or wrong. more › offshore wind (AR7): £89.49 (2024 prices) and £64.23 (2012 prices). official, DESNZ |
HPC: £129, fixed in real terms, 2025 prices. official, NAO The contract price is £89.50 (2012 prices), cut from £92.50 after SZC's final investment decision. official, NAO SZC has no contract price of this kind: it is paid through a regulated asset base. The NAO gives an “equivalent strike price” of £131–155 (summary) or £133–155 (paragraph 1.22), 2024-25 prices, and £152–178 without “the consumer subsidy” (the NAO's term). official, NAO The two NAO low ends differ; both are shown. The equivalent price converts a different mechanism and is not a contract price. |
| Contract length | Not published Risk and return records that the contract term is not confirmed from a document: the LCCCThe government-owned company that manages and pays out Contracts for Difference, and publishes the daily figures. more › data gives start dates and no end-date field (risk.html). |
HPC: 35 years from generation starting. official, NAO 2017 SZC: regulated asset base, paid by consumers through bills from after November 2025. official, NAO No contract length is in the research file. |
| Working life | 30 years for fixed offshore wind (22 years in the 2016 report). official, DESNZ generic assumption This is an assumption for a generic plant, not a published life for any Scottish farm. |
SZC: 60 years, as modelled by DESNZ. official A generic nuclear plant: 60 years in the 2016 report. official Torness: commissioned 1988; planned end of generation March 2030, which EDF gives as an estimate to be kept under review; the youngest advanced gas-cooled reactors were originally due to stop in 2023. press, EDF |
| Owner, and where the profits go |
Moray East: three owners, all outside the UK, traced through holding companiesA company that exists mainly to own shares in another company, often sitting between a wind farm and its ultimate owners. more ›; the Equitix holding company's register lists a Guernsey parent (75% or more) and also a UK-incorporated Equitix entity (more than 25%). 2025 dividendA payment a company makes to its shareholders out of its profits. more › £104.2m, 231% of that year's profit after taxA company's profit once tax has been deducted: the amount available to pay dividends or keep in the business. more ›, funded substantially from reserves. computed, from filed figures Beatrice: 40% held by SSE plc. Dividends £84.1m, 59.7% of profit after tax; of which £21.025m to Red Rock Power (China) and £14.7175m to TRIG, a Guernsey vehicle as reportedA number taken directly from a company's own accounts or a regulator's own published document, not calculated or estimated by this site. more ›. computed; the two payments as reported Dividends to owners outside the UK in the latest filed years: £139.9m, on the ownership described above. computed, from filed figures |
SZC shareholders: DESNZ 44.9%, La Caisse 20%, Centrica 15%, EDF 12.5%, Amber Infrastructure 7.6%. Equity up to £8.5bn, nominal. Expected post-tax equity return 10.8–13.0%, nominal. official, NAO The research file holds no dividend figures. HPC: built by NNB Generation Company (HPC) Limited, owned 66.5% by EDF and 33.5% by China General Nuclear Power Group (CGN). official, NAO 2017 Torness: EDF. |
| Who stands behind the loans |
Moray East: Japan's JBICJapan's state development bank, which lent directly to Moray East's construction financing. more › agreed in November 2018 to lend up to about £743m; Denmark's export credit agencyA foreign government body that guarantees loans to help its own country's exporters win contracts abroad. more › EKF was to guarantee part of the private banks' loan. press, JBIC's own release The wind farm's filed accounts do not name these lenders. Beatrice: 2016 financing from 13 commercial lenders and the European Investment Bank, with EKF guaranteeing £300m of the EIBThe European Investment Bank, a lender to some of the Moray Firth wind farm financing syndicates. more ›'s loan. press Refinanced in July 2019; the current lenders and any guarantee are not in the files held. filed These are foreign state bodies, not UK taxpayers. On the grid side, SSEN Transmission has an £800m UK National Wealth FundA UK government-owned investment body that can guarantee loans to infrastructure projects, backed by taxpayers. more › guarantee, undrawnA risk that only turns into an actual cost if something specific happens, such as a loan guarantee only being called on if the borrower defaults. more › at 31 March 2026. filed (risk.html) |
SZC: National Wealth Fund debt up to £36.6bn, nominal; commercial lenders £5bn, nominal; a proposed £5bn guarantee from France's export credit agency; government equity stake 44.9%, initial. Government and investors are committed to fund up to the higher regulatory threshold of £47.7bn, 2024-25 prices. official, NAO and DESNZ HPC: NNBG expected to finance the build in full from its two investors. official, NAO 2017 |
| Bill impact during construction | Not published No bill figure for a construction period is in the research files. LCCC lists Seagreen, Moray West and Inch Cape as not yet started, with no payment rows. official |
SZC: about £1 a month for a typical household, on average over construction. official, DESNZ SZC: £4 in 2025-26 on a typical household bill, building to a peak of £19–21 a year in the first decade of operation, 2024-25 prices. official, NAO HPC: the Department's estimate, reported by the NAO in 2017, was £10–15 a year of the average household bill up to 2030, in 2012 prices. official |
These sit outside the guaranteed price in the table above. The two columns are not like for like: the scopes differ, as each cell says.
| Item | Scottish offshore wind | Large nuclear |
|---|---|---|
| Grid built for it |
Scotland: £8.8–29bn of transmission built or approved. Figures as stated, in mixed price bases (2009-10 to 2023/24, one nominal outturn); two carry no price year. estimate Low: built projects (low) plus Eastern Green Link 1 and 2 and the Orkney link. High: built projects (high) plus Eastern Green Link 1, SSEN's £22bn programme and SPT's load-labelled lines. Low and high are not additive. The research file counts each line's whole cost; the share attributable toThe share of a group's profit allocated to a particular shareholder on paper, which is not the same as cash actually paid to them. more › wind is not quantified for most lines. Offshore transmission assets are inside the wind farm costs above, not counted here. |
Hinkley Connection (Hinkley–Seabank): OfgemThe UK government regulator for gas and electricity, which sets how much network companies can charge billpayers. more › capital cost allowance £655.7m, 2017/18 prices. official National Grid asked for about £716m. About £199/kW of HPC's contract capacity. estimate (655.7m ÷ 3,287.16 MW) Recovered through transmission charges over 45 years, not through the strike price. No outturn cost found. The scope is one 400 kV connection, 49 km overhead and 8.5 km underground. |
| Switch-off payments |
£1.9bn in 2025-26, Britain-wide. official, NAO 2024 prices in the NAO's text; its figure note says 2023-24 prices. The series covers payments to wind farms to turn down and to gas stations to turn up, so it is not Scotland-only or wind-only. In 2024/25 wind turn-down cost £370m and gas turn-up £910m. official Scottish offshore wind, calendar 2025: £181.32m of switch-off payments, which also sits inside the Britain-wide series (the periods differ). indicative, Elexon |
Not published No nuclear figure is in the research files. |
| Stability contracts |
Scotland, Stability Pathfinder Phase 2: £323m for 10 contracts with four companies, 10 years from April 2024; five synchronous condensers and five grid-forming batteries. official, NESO 2021 prices, undiscounted. NESOThe National Energy System Operator, the body that keeps Great Britain's electricity grid balanced minute by minute. more › links the need to “The imminent closure of nuclear power stations in Scotland and northern England, and the rising number of onshore and offshore wind farms in Scotland”. |
No £ figure NESO's 2023 siting note: “Nuclear (SMR) generation is a form of synchronous plant, which would support system stability requirements” where inverter-based supply dominates. The note is “highly indicative” and is about small reactors. official, NESO NESO: “Stability has traditionally been supplied as an inherent by-product of synchronous generation.” No figure was found for inertia or fault-level contribution from a large reactor. |
| Largest single loss | Not published No equivalent figure is in the research files. |
NESO: “The minimum inertia of 102 GVA.s is based on a future largest loss of 1800 MW”. official, NESO Frequency Risk and Control Report, May 2025 Ofgem asked NESO for more information on the 102 GVA.s proposal on 12 December 2025; the outcome was not found. NESO also says: “As our largest loss size increases, with sites such as Hinkley-C power station connecting to the network in the future” it expects a significant increase in response requirements. official, NESO The file does not say 1,800 MW is Hinkley's own size. NESO recommends an additional 200 MW of DC-Low response. No £ figure was found. |
| Decommissioning and waste |
Operators pay under the Energy Act 2004 “polluter pays” regime; Beatrice is already accruing a provision (risk.html). filed DESNZ's generic assumption for fixed offshore wind: £265,200/MW, 2024 prices, medium case, inside its cost of generation. official This is not a published figure for any Scottish farm. |
Funded Decommissioning Programme. New nuclear operators must have secure financing for the full cost of decommissioning and their full share of waste management and disposal. official, DESNZ HPC: about £2/MWh inside the strike price (price year not stated). official, DESNZ NNBG's estimate of decommissioning and waste costs is £7.3bn, 2016 prices. official, NAO SZC: £2.3–2.5bn real (2024-25 prices) paid into an investment fund over the operating life. official, NAO NDA legacy provision: £114.5bn, discounted, at 31 March 2026. official, NDA This belongs to older stations, not to HPC or SZC. Torness is one of seven advanced gas-cooled stations not yet in it; £22bn undiscounted is a contingent figure for the seven together, estimated by their current owner. official, NDA |
| Is the cost published? |
No, for three items: vessel day ratesThe charge for hiring a vessel, including its crew, for one day; rarely published for offshore wind contracts. more ›, contract values and the capital cost of Shetland HVDCHigh Voltage Direct Current: the technology used for long subsea electricity cables, including the Shetland link. more › Link 2 are not published. Notices name vessels and jobs but give no rates or values; SSEN, Ofgem and NESO have published no cost for the link. official (real-cost.html, shetland2.html) |
Totals are published by the NAO. But DESNZ withholds project costs as “commercial sensitivity”. DESNZ, Electricity Generation Costs 2025, lines 1200–1202 of sources/crawl/assets.publishing.service.gov.uk/media/gencosts2025/electricity-generation-costs-report-2025.txt:
The next paragraph of the same report says: “High-level cost assumptions for both Hinkley Point C and Sizewell C are in the public domain.” (G25:1204) |
Sources: research/NUCLEAR-COMPARISON.md (sections 1, 2, 4 to 9); research/SCOT-OFFSHORE-COST-1-CAPEX.md, -2-TRANSMISSION.md, -3-STABILITY.md, -4-RUNNING.md; counter/real-cost.html and counter/risk.html for the figures already on this site. Scotland's 2019–2024 offshore wind load factors are not in the files held: DESNZ's 2025 article tabulates 2025 only, and the load-factor spreadsheet it refers to is not held. The research file's own estimates for those years (48.6, 44.8, 33.8, 42.5, 25.2 and 23.2%) use the average of opening and closing capacity and may be biased either way where capacity was added during the year.
The 2025 DESNZThe UK government department responsible for energy policy, including subsidy auctions and community fund guidance. more › report gives offshore wind £103/MWhUnits of electrical power (MW) and energy (MWh, GWh): power is a rate, energy is power delivered over time. more › for projects commissioning in 2030 and £98 for 2035, in 2024 prices. It gives no nuclear figure. The latest DESNZ/BEIS report found with both on one basis is from 2016, in 2014 prices: nuclear £95, offshore wind £100.
| Report | Price year | Commissioning | Large nuclear, £/MWh | Fixed offshore wind, £/MWh | Class |
|---|---|---|---|---|---|
| DESNZ, Electricity Generation Costs 2025 | 2024 | 2030 | not published | 103 | official |
| 2035 | not published | 98 | official | ||
| BEIS, Electricity Generation Costs, November 2016 | 2014 | 2025 | 95 (first-of-a-kind PWR) | 100 (Round 3) | official |
| 2030 | 78 (nth-of-a-kind) | 96 | official |
The 2016 report is old. Its nuclear cost was a first-of-a-kind estimateLabels on the evidence register showing how strong a figure's source is: an official document, a press report, arithmetic, or an estimate. more › set before HPC's cost rises, and its offshore wind life of 22 years is below today's 30. The 2020 report says it carries the 2016 nuclear assumptions forward; the 2023 report uses them together with publicly available Hinkley Point C data. The two rows of the table are different bases and are not mixed.
On what the comparison leaves out, the 2016 report says:
“As the definition of levelised costs relates only to those costs accruing to the owner/operatorThe company that owns or charters out a ship, as distinct from the client paying to use it for a particular job. more › of the generation asset, it does not cover wider costs that may in part fall to others, such as the full cost of system balancing and network investment, or air quality impacts.”
official · BEIS, Electricity Generation Costs, November 2016 · G16:256–259
The 2025 report lists the same thing under “Out of scope”:
“Wider system costs beyond those faced by the developer, and wider system benefits of deploying generation assets. These cannot be assessed without whole power system modelling.”
official · DESNZ, Electricity Generation Costs 2025 · G25:266–268
DESNZ's own reasoning, as reportedA number taken directly from a company's own accounts or a regulator's own published document, not calculated or estimated by this site. more › by the NAO (paragraph 1.23): its modelling shows “the greater cost of generation is outweighed by other benefits”, because standard metrics “do not capture wider system costs associated with intermittent generation, such as transmission costs, reserve generation capacity and other balancing services”. That is a modelling claim, not a measured outcome. The NAO also records that the benefits depend on events several decades ahead, with a break-even point “not until 2064 in the most favourable of the core scenarios”. official, NAO
illustration · estimate This is a simple model, not a forecast of any project. The starting values are placeholders chosen for the illustration. They are not published figures for any wind farm or power station. Change them and the results update.
Working: switch-on in 2024. Output 17.87 TWh a year. MarginA profit figure expressed as a percentage of revenue, showing how much of each pound of income is kept as profit. more › after running costs £1.34bn a year.
illustration, estimate · results shown are for the starting values
| Savings arrive | At 3.5% | At 5% | At 7% |
|---|---|---|---|
| All savings | £377bn | £563bn | £910bn |
| Half | £780bn | £1,038bn | £1,509bn |
| None | £1,182bn | £1,513bn | £2,108bn |
Inputs, official: the Climate Change Committee's Seventh Carbon Budget costing data, sheet “Whole economy charts”, rows 165 and 166, 2025 to 2050. Additional capital spend sums to £670.1bn; net operating cost sums to −£562.2bn (a negative figure is a saving). Prices as in the CCC data, 2023. Each year: balance = balance × (1 + r) + capital spend + the share of the saving that arrives.
Caveats. It treats all investment as financed and rolled up; in practice part is paid in cash. It does not count the value of the assets in 2050. It is UK-wide and covers all sectors, not Scotland or power only. It excludes spending before 2025. The CCC itself presents a net cost, not a financed balance. Working in research/NETZERO-DEBT-2050.md.
All of this is an illustration, estimate. It shows how the numbers interact: with the starting values the yearly margin is smaller than the yearly interest, so the debt grows after switch-on.
A checklist of what the research files say. A statement about one kind of plant is not carried over to the other. Where the files hold nothing, the cell says so.
| Question | Wind | Nuclear | Source |
|---|---|---|---|
| Runs whatever the weather | Observed share of time running, 2025: Scottish offshore wind 23.5%; UK offshore wind 36.1%. official The files record no statement of cause for the Scottish figure. DESNZThe UK government department responsible for energy policy, including subsidy auctions and community fund guidance. more ›, as reportedA number taken directly from a company's own accounts or a regulator's own published document, not calculated or estimated by this site. more › by the NAO, refers to “wider system costs associated with intermittent generation” when comparing SZC with renewables (see section 3). |
Observed share of time running, 2025: Torness 82%; UK nuclear fleet 64.04%, lower in 2025 after an extended outage at Hartlepool. press, official DESNZ says SZC has the technical capability for load-following but models it as baseload, because it is unclear whether that will be used. official |
NUCLEAR-COMPARISON.md sections 5, 6 and 9c; NAO paragraph 1.23 |
| Steadies frequency (inertia) | NESOThe National Energy System Operator, the body that keeps Great Britain's electricity grid balanced minute by minute. more ›: “Renewables like wind and solar don't synchronise with the grid in a way that provides inertia”. NESO buys inertia from other sources: Scotland's Phase 2 contracts are five synchronous condensers and five grid-forming batteries. official, NESO |
NESO's 2023 siting note: “Nuclear (SMR) generation is a form of synchronous plant, which would support system stability requirements” where inverter-based supply dominates. The note is “highly indicative” and covers small reactors. official, NESO In the ONR's assessment of one small-reactor design (BWRX-300), the requesting party said it could not meet two Grid Code requirements with the current design, one of them frequency response. official, ONR No figure for a large reactor was found. |
SCOT-OFFSHORE-COST-3-STABILITY.md sections 2 and “Context”; NUCLEAR-COMPARISON.md section 6 |
| Supports fault level | NESO: “large coal and gas generation create five times more fault current compared to wind and solar”. The £323m Phase 2 contracts “primarily solve insufficient Short Circuit Levels” in Scotland. official, NESO |
The same 2023 NESO note treats nuclear (SMR) as synchronous plant that supports stability. NESO says fault level “helps us to maintain system voltage”. official, NESO No figure for fault-level contribution from a large reactor or an advanced gas-cooled reactor was found. |
SCOT-OFFSHORE-COST-3-STABILITY.md; NUCLEAR-COMPARISON.md sections 6 and 10 |
| Can restart a dead grid (black start) | No source found The research files hold no statement either way for wind. A northern-regions restoration tender of £53.8m (eight contracts) covers the North West, North East and Scotland; the providers and the Scottish share are not published. official, NESO |
No source found No NESO or ONR statement that nuclear can, or cannot, provide black start was found. NESO says a provider must be able to start from an on-site auxiliary generator without external supplies. official, NESO |
NUCLEAR-COMPARISON.md sections 6 and 10 (item 6); SCOT-OFFSHORE-COST-3-STABILITY.md section 2d |
| Needs backup in calm weather | Not stated in these terms in the research files. DESNZ's reasoning, as reported by the NAO, refers to “reserve generation capacity and other balancing services” associated with intermittent generation. That is a modelling claim, not a measured outcome. official, NAO |
Not stated in the research files. DESNZ models SZC as baseload at 90%; nuclear fleet output ranged from 56.82% to 72.85% across 2018–2025. official No reserve or balancing cost attributable toThe share of a group's profit allocated to a particular shareholder on paper, which is not the same as cash actually paid to them. more › large nuclear units was found. |
NAO paragraph 1.23, as quoted in NUCLEAR-COMPARISON.md section 9d; NUCLEAR-COMPARISON.md sections 5b and 6 |
| Needs grid reinforcement far from demand | DESNZ: “a plant built a long distance from centres of high demand will increase transmission network costs”. official Scottish transmission built or approved: £8.8–29bn (section 2). North Scotland carries the highest generation transmission tariff of the 27 zones for conventional plant: £36.182993/kW in NESO's 2025/26 example for low-carbon plant such as nuclear (75% load factor). official, NESO |
Hinkley Connection: OfgemThe UK government regulator for gas and electricity, which sets how much network companies can charge billpayers. more › allowance £655.7m, 2017/18 prices, recovered over 45 years. official NESO: “The total amount of generation connected to any one point cannot exceed the amount of response available.” official Whether HPC is near or far from demand is not stated in the research files. |
NUCLEAR-COMPARISON.md sections 4, 6 and 7; SCOT-OFFSHORE-COST-2-TRANSMISSION.md; FACT-SHEET.md fact 28 |
| Date | Whole-project cost | Price year | Unit 1 start, as then stated | Class |
|---|---|---|---|---|
| July 2016, final investment decision | £18bn | 2016 prices | 2025 (end of year); the NAO's “original” date was 2023 | official, NAO |
| 3 July 2017 | £19.6bn | not stated in the saved article | by the end of 2025 | press |
| 25 September 2019 | £21.5–22.5bn | 2015 sterling, excluding interim interest | end of 2025 | press, EDF release |
| 27 January 2021 | £22–23bn | 2015 prices | June 2026 | press |
| 20 May 2022 | £25–26bn | 2015 prices | June 2027 | press |
| 23 January 2024 | £31–34bn, plus £1bn in a third scenario | 2015 prices | 2029, 2030 (base case) or 2031 | press |
| February 2026, EDF 2025 results | £35–36bn | 2015 prices | 2030 to 2031; unit 2 2031 to 2032 | official, NAO table citing EDF |
The £18bn and £35–36bn are in different price years (2016 and 2015) and have not been re-based. The NAO's earliest entry is £17.9bn in 2015 prices. The EDF group's own statements were not retrievable; rows between 2017 and 2024 rest on trade press and an EDF release. No NAO value-for-money report on HPC after June 2017 was found.
SZC's baseline is £38.2bn with the plant fully operational in July 2039. DESNZThe UK government department responsible for energy policy, including subsidy auctions and community fund guidance. more ›'s lower regulatory threshold is £40.5bn, October 2039; the higher is £47.7bn, August 2043. All are in 2024-25 prices. official, NAO The final investment decision was on 22 July 2025. These are forecasts at that date, not an outturn.
| Measure | Forecast in 2010 | Outturn |
|---|---|---|
| The increment caused by the rule | Central £195m present value over 2010–20, 2009 prices, about £18m a year. Range £160m to £992m. official, forecast | Attributed to the rule by National Grid, reported by OfgemThe UK government regulator for gas and electricity, which sets how much network companies can charge billpayers. more ›: £4.4m (Apr 2011 to Aug 2012); £22.2m (Sep 2012 to Sep 2013); £69.4m (Oct 2013 to Sep 2014); £121.7m (Oct 2014 to Sep 2015). Not reported after 2015 in the files held. official |
| The total of all constraint costsMoney paid to a generator to switch off, or reduce output, because the grid cannot carry all the power it is producing. more › | Central £999m present value over 2010–20. Range £571m to £2,019m. official, forecast | NAO thermal constraint costs by year, £bn: 0.56 (2018-19), 0.52, 0.65, 1.21, 1.04, 1.54, 1.65, 1.90 (2025-26). 2024 prices in the NAO text; 2023-24 prices in its figure note. official |
Not like for like. The forecast is the increment over the alternative rule; the outturn series is the total. The forecast is a present value in 2009 prices; the outturn is annual, in 2023-24 or 2024 prices. Only 2018-19 and 2019-20 fall inside the forecast window. Read side by side, not subtracted. Ofgem's sixth monitoring report (December 2015) said National Grid expected these costs to “drop to nearly zero in 2017/18”; the NAO says Ofgem forecast they would fall to zero by 2023-24. Detail on the real cost page.
Ofgem's stated need case was three prospective wind farms. Press reporting of NESOThe National Energy System Operator, the body that keeps Great Britain's electricity grid balanced minute by minute. more ›'s 2024 recommendation put them at 2.8GW. press In March 2026 the 500MW Arven South option was handed back to Crown Estate Scotland, its board citing “specifically the lack of a viable grid connection”; Ocean Winds keeps its lease for the larger 1.8GW Arven site. press That leaves 2.3GW: Arven 1.8GW and Stoura 500MW. press The capital cost of Link 2 is not published. See the Shetland link page.
Project research files, compiled 4 and 5 October 2026: research/NUCLEAR-COMPARISON.md; research/SCOT-OFFSHORE-COST-1-CAPEX.md, -2-TRANSMISSION.md, -3-STABILITY.md and -4-RUNNING.md; research/CONNECT-AND-MANAGE.md; research/NETZERO-DEBT-2050.md; FACT-SHEET.md facts 22, 26 and 28; and the figures already on this site in real-cost.html and risk.html. PrimaryLabels on the evidence register showing how strong a figure's source is: an official document, a press report, arithmetic, or an estimate. more › sources behind them: NAO, Sizewell C (HC 33), 20 May 2026, and Hinkley Point C (HC 40), 23 June 2017; DESNZThe UK government department responsible for energy policy, including subsidy auctions and community fund guidance. more › Electricity Generation Costs 2025 and its Annex A, and the BEIS Electricity Generation Costs report of November 2016; DESNZ Sizewell C final investment decision press release and value-for-money assessment, July 2025; DESNZ Regional Renewable Statistics, 2025; DUKES 2026 tables 5.10.B, 5.11 and 6.3; EDF Energy fleet update for 2025, its release on the Hinkley Point C project of September 2019, and its Torness material; OfgemThe UK government regulator for gas and electricity, which sets how much network companies can charge billpayers. more › decision on the Hinkley–Seabank project, May 2020; NESOThe National Energy System Operator, the body that keeps Great Britain's electricity grid balanced minute by minute. more › Frequency Risk and Control Report, May 2025, the Stability Pathfinder Phase 2 results of April 2022 and NESO's 2023 nuclear siting note; ONR assessment of the BWRX-300 electrical engineering design; NDA Annual Report and Accounts 2025/26; DESNZ Hinkley Point C Funded DecommissioningThe legal duty to remove offshore energy infrastructure and restore the site once it stops being used, paid for by the operator. more › Programme; Low Carbon Contracts CompanyThe government-owned company that manages and pays out Contracts for Difference, and publishes the daily figures. more › data; Elexon indicative balancing data for 2025; DECC impact assessment URN 10/899, 27 July 2010, and Ofgem connect and manage monitoring reports 2011 to 2015; Climate Change Committee, Seventh Carbon Budget costing data, May 2025; filed company accounts for the wind farms. Also relied on directly by this page: NAO, Upgrading the electricity transmission network (HC 589), 11 September 2026; DESNZ Reformed National Pricing delivery plan, 2026; DESNZ Contracts for DifferenceA government contract that tops up a wind farm's income when the market price is low, and claws money back when it is high. more › Allocation RoundOne of the periodic government auctions at which Contracts for Difference are awarded to competing projects. more › 7 results; guidance on decommissioning offshore renewable energy installations under the Energy Act 2004, March 2019; World Nuclear News articles of 3 July 2017, 27 January 2021, 20 May 2022 and 23 January 2024; Shetland News, 19 March 2024 and 20 March 2026; Ofgem tCSNP2Ofgem's transitional Centralised Strategic Network Plan 2 process, under which this project was assessed and put in the delivery track. more › consultation, 1 August 2024; Ofgem Frequency Risk and Control Report 2025 decision, 12 December 2025; Ofgem's Hinkley Point C grid link announcement; NESO Final TNUoSTransmission Network Use of System charges: the part of a bill that pays for building and running the high-voltage grid. more › Tariffs 2025/26, its black start guide, its northern-regions restoration services release and its explainer on grid stability; JBICJapan's state development bank, which lent directly to Moray East's construction financing. more ›'s Moray East release, November 2018; IJGlobal and Pinsent Masons on the Beatrice financing, 2016; Red Rock Power's Inch Cape financial close release, January 2025; SSE plc Annual Report 2026; the Companies HouseThe UK government registry where companies file their accounts and ownership details, most of which the public can read for free. more › register of persons with significant control. Full file and line citations are in the research files. Related pages: who pays, the missing figures, the evidence register.