Where Great Britain electricity stands in May 2026: live state, capacity margin, AR7 results and the Clean Power 2030 path

Where Great Britain electricity stands in May 2026

The electricity system in May 2026 sits inside a window of unusually dense procurement and reform. Six of the load-bearing commitments below have been decided, cleared or had their first operational result inside the last twelve months. The current state is set out in one section so the rest of the page reads as one continuous brief rather than a stack of unrelated topics, and so the live dashboard further down has the context the half-hourly numbers need to make sense.

The Capacity Market T-4 auction for the 2029 to 2030 delivery year cleared on 25 February 2026 at twenty seven pounds ten per kilowatt year, procuring 40.1 gigawatts of de-rated capacity against a target of 39.4 gigawatts.¹ The T-1 top-up auction for 2026 to 2027 cleared at five pounds per kilowatt year for 7.2 gigawatts. Contracts for Difference Allocation Round 7 reported on 14 January 2026 and awarded a record 8.4 gigawatts of offshore wind alongside the smaller AR7a budget for solar, onshore wind and emerging technologies.⁶ NESO issued the Connections Reform Gate 2 detailed results in April 2026 with 283 gigawatts of generation and storage and 99 gigawatts of demand progressed to firm offers across Phase 1 to 2030 and Phase 2 to 2035.⁷

The headline policy commitment is Clean Power 2030. The DESNZ and NESO action plan published on 5 December 2024 set a target of 95 percent low-carbon electricity by the end of 2030, with up to 5 percent of annual energy from unabated gas retained as a resilience buffer for low-renewables weeks. The action plan is a megawatts-per-year build trajectory across offshore wind, onshore wind, solar, batteries, long-duration storage, interconnectors and hydrogen-ready dispatchable plant. The procurement cadence is annual through the Capacity Market and biennial through Contracts for Difference. AR7 in January 2026 and the T-4 clearing in February 2026 are the first procurement results that confirm whether the trajectory is on track. Both came in at the upper end of the action plan range.

The data layer that lets a planner or a market participant follow the trajectory is moving too. The Long Term Development Statement published its Stage 2 on 29 May 2026 under the third Ofgem derogation letter of 13 May 2026, with the BSI CIM Engagement Hub confirmed as the official location of record for LTDS data-exchange definition artefacts.⁸ The Carbon Intensity API has been the standing public reference for the half-hourly carbon-intensity nowcast since 2017 under CC BY 4.0; PV_Live has been the public reference for the half-hourly solar nowcast since 2014 under CC BY 4.0; the NESO Data Portal carries the half-hourly generation by fuel type under the NESO Open Licence with the required attribution.^{2 4 5 3}

So the current state of the electricity domain in May 2026 has a settled high-level architecture (NESO at the centre, Reformed National Pricing chosen over zonal pricing under the summer 2025 REMA decision, strategic planning under SSEP and CSNP), a fresh set of procurement results that the action plan can build against, and a public data layer dense enough that the live state can be read minute by minute without privileged access. The pages below go through each.

The live state, in fifty hertz

The Great Britain electricity system is held within plus or minus 0.2 hertz of 50.00 hertz by NESO from the Electricity National Control Centre in Sindlesham. Live data on what is generating, what is being imported, and what carbon-intensity the megawatt is carrying flows from three public sources: the Elexon Balancing Mechanism Reporting Service for generation by Balancing Mechanism Unit and demand, the Carbon Intensity API for emissions in grams of carbon dioxide per kilowatt-hour at the national and regional level, and the NESO Data Portal for inertia, frequency response, constraint volumes and Demand Flexibility Service results. All three are free, open, and update on a sub-hourly cadence.^{5 2 3}

The dashboard immediately below renders these three pipelines into one view. Generation by fuel type comes from the NESO Data Portal half-hourly historic-generation-mix dataset under the NESO Open Licence with attribution "Supported by National Energy SO Open Data".³ Carbon intensity comes from the api.carbonintensity.org.uk endpoint under CC BY 4.0 with attribution to the National Grid ESO Carbon Intensity API.² Solar generation comes from the PV_Live API published by the University of Sheffield under CC BY 4.0 with attribution to Sheffield Solar.⁴ A planner reading the dashboard live during a windy May afternoon can see the share of demand met by wind run above 60 percent, the carbon intensity drop into the low double digits, and the solar generation curve trace the diurnal cycle as the day moves past noon.

The three pipelines have different licences and different cadences, and the dashboard makes that explicit in its source register. The NESO Open Licence is derived from the Open Government Licence v3.0 with NESO-specific attribution.³ Both Carbon Intensity and PV_Live use CC BY 4.0; their licence terms are kept on the respective owners' landing pages.^{2 4} A consumer of the live data who wants to redistribute the numbers needs to satisfy all three attribution requirements, not just one.

Behind the dashboard's headline number sits the half-hourly settlement period. The Balancing and Settlement Code is the contractual frame that turns each metered megawatt-hour into a settled cash position over the following months under the R1, R2, RF and DF run cadence. Market-wide Half Hourly Settlement reached Milestones M10 to M13 in early 2026 with ten million Meter Point Administration Number initiations completed; the programme cuts over in July 2027, after which every domestic consumer's electricity is settled at the half-hourly level rather than against a profile.

The dispatchable margin behind Clean Power 2030

The Clean Power 2030 commitment is not a renewable build-out target on its own. It is a megawatt envelope that holds three distinct procurement mechanisms in balance. Variable renewables (offshore wind, onshore wind, solar) deliver the bulk of the energy. Firm low-carbon plant (nuclear, hydrogen-ready dispatchable, long-duration storage) backs the renewables when the weather pattern reduces variable output. Unabated gas sits as the resilience margin, capped at 5 percent of annual energy under the action plan, and called on in the rare weeks when neither variable renewables nor firm low-carbon are sufficient. The Capacity Market is the mechanism that procures the dispatchable layer; Contracts for Difference is the mechanism that procures the variable-renewable layer; long-term decisions on nuclear and small modular reactors handle the firm low-carbon layer outside the annual auction cycle.

A planner working back from the 2030 target needs four numbers per delivery year: the annual energy demand forecast (around 285 to 300 terawatt-hours through to 2030, lifted by EV charging, heat pumps and data centres), the de-rated dispatchable capacity required to cover peak demand at the 1-in-20 winter standard, the contracted volume of variable renewables expected to deliver on an annual energy basis, and the residual unabated-gas energy that the resilience margin allows. The February 2026 T-4 clearing pinned the first number for 2029 to 2030: 40.1 gigawatts at twenty seven pounds ten per kilowatt year, against a 39.4 gigawatt target.¹ The January 2026 AR7 result pinned the second number for the same year: 8.4 gigawatts of new offshore wind on top of the existing variable-renewable fleet.⁶

The reading from the two clearings is that the procurement machinery is moving at the cadence the action plan needs. The T-4 cleared 1.8 percent above target at a clearing price below the prior year's T-4 in real terms. The AR7 award was the largest offshore-wind allocation in any single round in the GB regime. The Connections Reform Gate 2 process in April 2026 added 283 gigawatts of generation and storage to the firm-offer pipeline across the two delivery phases, which is the capacity envelope inside which the next four years of procurement results will sit.⁷ The remaining question is whether the build-out keeps pace with the procurement, and whether the supply chain absorbs the AR7 award on the contracted delivery schedule.

The build-out risk that sits underneath the procurement numbers

A procurement result is a contract, not a megawatt. AR7 awarded 8.4 gigawatts of offshore wind that needs port capacity for installation vessels, monopile fabrication slots, blade manufacturing capacity, cable laying schedules, and grid connection delivery against the Gate 2 offer windows. The T-4 clearing buys de-rated dispatchable capacity that needs new-build CCGTs or battery storage or hydrogen-ready plant to come into operation by the end of September 2029. Both supply chains are stressed across the North Sea, with similar procurement rounds in Germany, the Netherlands, Denmark, Norway and Poland competing for the same vessel days and the same blade slots. The procurement headline is solid; the build risk underneath it is where the trajectory becomes harder to read.

The annual energy split that the action plan profiles

The 95 percent target reads more clearly as four annual energy splits rather than as a single share. Variable renewables (offshore wind, onshore wind, solar) provide around 60 to 65 percent of the annual energy under the action plan profile, with the offshore-wind share rising from around 16 percent of annual generation in 2024 to roughly 35 to 40 percent in 2030 as the AR rounds commission. Nuclear holds at around 12 to 15 percent through to 2030, with Hinkley Point C entering service from 2027 and the existing fleet retiring on a defined schedule (Hartlepool 2026 to 2027, Heysham 1 2026 to 2027, Heysham 2 and Torness 2028, Sizewell B running to 2055). Firm low-carbon dispatchable (long-duration storage, hydrogen-ready CCGTs, demand-side flexibility, interconnector imports) takes the remaining 15 to 20 percent of the low-carbon share. Unabated gas sits at the 5 percent residual.

Reading the procurement results against the annual energy split gives a clearer view of progress than reading the capacity total alone. The 40.1 gigawatts of T-4 cleared in February 2026 is a de-rated number; the same volume on a nameplate basis is around 50 to 55 gigawatts. The 8.4 gigawatts of AR7 offshore wind is a nameplate number; the same volume on an annual energy basis is around 35 to 40 terawatt-hours assuming a 45 percent load factor for fixed-bottom offshore in Great Britain waters. Both translations need a worked check against the delivery year's demand forecast, the contracted renewable energy zero-bid stack, and the merit-order economics for the dispatchable layer. The action plan publishes the relevant range; the procurement results confirm the lower bound of the range is being met.

The Capacity Market clearings for 2029 to 2030 and 2026 to 2027

The Capacity Market is the procurement mechanism that buys the obligation to be available at peak demand. The auction cadence is annual. The T-4 auction procures four years ahead of delivery; the T-1 top-up procures one year ahead. Capacity is de-rated by technology class to reflect contribution to peak (a battery's de-rating factor depends on its duration; a CCGT's de-rating factor is close to unity; an interconnector's depends on the simultaneous import availability on the linked system). The clearing price is uniform: every successful bid earns the auction's marginal price for the full delivery year.

The 2029 to 2030 T-4 auction cleared on 25 February 2026 at twenty seven pounds ten per kilowatt year, procuring 40.1 gigawatts of de-rated capacity against a target of 39.4 gigawatts. The clearing price is below the 2028 to 2029 T-4 (which cleared at sixty pounds per kilowatt year in 2024 to 2025), reflecting an increase in firm-offer pipeline behind the auction and the maturing of battery-storage bids into the merit order. The auction included demand-side response and aggregator-led volumes alongside the conventional CCGT, battery and pumped-hydro classes. The T-1 top-up for 2026 to 2027 cleared in March 2026 at five pounds per kilowatt year for 7.2 gigawatts against a 6.3 gigawatt target.¹

A capacity provider that won at the T-4 has the obligation to be available at peak demand from the first day of October 2029, with penalty exposure for non-delivery under the auction rules. A new-build CCGT that won a capacity agreement uses the obligation as the financing backstop for the engineering procurement and construction contract. A battery developer uses the agreement to underwrite the project finance against the merit-order revenue stack. The reading from the cleared volumes is that the procurement machinery accepted firm-offer volumes from a queue that was rebuilt under the Gate 2 process; the T-4 entry volume of 44 gigawatts against a 39.4 gigawatt target gave the auction headroom that the prior year's auction did not have.

Contracts for Difference Allocation Round 7 results

Contracts for Difference are the primary support mechanism for new low-carbon generation in Great Britain. A successful CfD bidder agrees a fixed strike price (in pounds per megawatt-hour, real 2012 prices for legacy rounds, real 2024 prices for AR7) for a contract term of 15 years from commissioning. When the market reference price for the contracted output sits below the strike, the CfD counterparty (Low Carbon Contracts Company Limited) pays the difference to the generator. When the market reference price sits above the strike, the generator pays the difference back. The contract therefore hedges the generator's revenue and lets long-dated low-carbon investment proceed without exposure to wholesale price volatility.

AR7 reported on 14 January 2026 and awarded a record 8.4 gigawatts of offshore wind, the largest offshore-wind allocation in any single round in the GB regime since CfDs began under the Energy Act 2013.⁶ The AR7a top-up round for solar, onshore wind and emerging technologies (tidal stream, floating offshore, geothermal) followed with the budget envelope published in the same announcement. The DESNZ statement framed the result as the procurement step that the Clean Power 2030 trajectory needed; the offshore-wind volume specifically is the variable-renewable build-out that the action plan profiled for the 2030 commitment year.

The next AR round is expected on the established biennial cadence in 2027. The AR7a top-up runs in 2026. The CfD counterparty's contract register on lowcarboncontracts.uk publishes each award with the contract term, the strike price and the technology class once the award is confirmed under the Allocation Framework.

Why the AR7 offshore-wind result lifted the procurement curve

Before AR7, the offshore-wind allocation per round had been sliding for three rounds in a row against a rising target. AR4 (July 2022) had delivered 7.0 gigawatts at a strike of 37.35 pounds per megawatt-hour (real 2012 prices). AR5 (September 2023) had cleared no offshore-wind volume because the administrative strike price had been set below the level at which projects could clear; the result was politically read as a stalling of the offshore-wind build-out. AR6 (September 2024) had recovered with 5.3 gigawatts at a higher administrative strike, but the rate of delivery against the action plan was still under question. AR7 reset the curve: the 8.4 gigawatts cleared was the largest single-round volume since CfDs began, and the administrative strike price was set against the prevailing North Sea cost stack.

The supply chain implication of an 8.4 gigawatt award is roughly 24 to 28 new monopile foundations, 84 to 100 14-megawatt turbines or 60 to 75 18-megawatt turbines (depending on the selected hardware), several new export cable runs into the onshore substations contracted under the Grid Code and the Connection and Use of System Code, and a delivery schedule that aligns commissioning between 2028 and 2031. The grid connection step is the slowest item on the project critical path; the Gate 2 offer windows that NESO opens between March and November 2026 are the contractual point at which the offshore-wind project secures the network capacity its contract is built against.

The generation mix as Great Britain entered 2025

The 2024 generation mix is the baseline against which the Clean Power 2030 trajectory is read. Total Great Britain generation in 2024 was 285.0 terawatt-hours, down 3.1 percent on 2023 on a weather-corrected basis. Renewables crossed 50 percent of annual energy for the first time in any calendar year, at 50.4 percent. Wind delivered 29.2 percent and overtook gas as the single largest source. The last operational coal plant, Ratcliffe-on-Soar in Nottinghamshire, ran its final cycle and went offline at midnight on 30 September 2024, ending 142 years of coal-fired electricity in Great Britain that began at the Holborn Viaduct station in January 1882. Low-carbon generation (renewables plus nuclear) was 64.7 percent of the annual total, or 184.3 terawatt-hours.⁵

Two operational records sit alongside the annual share. Carbon intensity averaged 124 grams of carbon dioxide per kilowatt-hour across 2024, a record low. The system logged 64.5 hours of demand fully covered by clean energy across the year (zero coal, gas only as backup outside the operational window) and beat that figure inside the first four months of 2025 with more than 87 hours of 100 percent clean operation by April.

The headline question for the 2026 and 2027 picture is whether the variable-renewable share continues to lift while the dispatchable layer rotates from unabated gas to the cleared T-4 mix of batteries, pumped hydro, demand-side response and the residual CCGT fleet. The T-4 clearing buys the obligation to be available; the energy mix in each delivery year depends on the weather pattern and the merit-order economics in real time. A windy 2030 will see the dispatchable layer dispatched less; a low-wind 2030 will see it dispatched more, against the 5 percent annual-energy cap on unabated gas under the action plan.

Imports, exports and the interconnector layer in the 2024 picture

Net imports across the interconnector layer hit a record 33.4 terawatt-hours in 2024, around 11.7 percent of annual generation. The operational interconnector capacity sits at around 10.3 gigawatts across ten cross-border links: IFA1 (France), IFA2 (France), BritNed (Netherlands), Nemo Link (Belgium), North Sea Link (Norway), ElecLink (France via the Channel Tunnel), Viking Link (Denmark, the longest subsea cable in service), the Moyle Interconnector (Northern Ireland), the East-West Interconnector (Ireland), and Greenlink (Ireland). The Cap and Floor regulatory framework administered by Ofgem governs interconnector revenue and floor support; the next regulatory window covers further pipeline links toward roughly 18 gigawatts of operational capacity by 2030.

The economic effect of the import layer is to flatten the wholesale price curve in the windows when Great Britain prices sit above the linked-system prices, and to lift it when they sit below. The 2024 record reflects two structural factors: the lower carbon intensity and lower marginal cost of the Norwegian hydro and French nuclear fleets in the linked systems, and the slightly slower offshore-wind build-out in Great Britain through the AR5 round than the action plan had profiled. A consumer reading the import layer needs to understand that an imported megawatt-hour carries the carbon intensity of the linked system at that half-hour, not the Great Britain grid intensity; the Carbon Intensity API has a flag in the half-hourly payload to identify the import contribution and its imputed intensity.

The carbon intensity trajectory and the 95 percent commitment

Carbon intensity is the half-hourly measure that joins the generation mix to the emissions account. The Carbon Intensity API published by NESO with Oxford and EDF since 2017 carries the national nowcast and a regional split across 14 regions, updated on a 30-minute cadence, with a 48-hour ahead forecast.² The API runs on the api.carbonintensity.org.uk endpoint under CC BY 4.0 with attribution to the National Grid ESO Carbon Intensity API. The half-hourly value reflects the fuel mix dispatched at that settlement period multiplied by the lifecycle emissions factor for each fuel: zero for wind, solar and hydro at point of generation; around 12 grams per kilowatt-hour for nuclear on a lifecycle basis; around 380 grams per kilowatt-hour for gas on a lifecycle basis; around 230 grams per kilowatt-hour for biomass on the official lifecycle accounting under the action plan.

The trend across the last five calendar years has been a step change downward. The 2020 annual average was around 180 grams per kilowatt-hour. The 2024 annual average was 124 grams per kilowatt-hour, the lowest year on record. Operational lows of below 30 grams per kilowatt-hour are now routine on windy spring afternoons, and the system has logged 87 hours of 100 percent clean operation inside the first four months of 2025. The Clean Power 2030 commitment translates the annual percentage to a carbon intensity floor: a 95 percent low-carbon energy share with 5 percent unabated-gas residual implies an annual carbon intensity in the low 20s of grams per kilowatt-hour on a generation-weighted basis.

A consumer-facing reading of the trajectory is that an electric vehicle charging on the grid at 124 grams per kilowatt-hour today emits roughly a third of what an equivalent petrol vehicle emits over the same journey, before accounting for the well-to-wheel difference. A heat pump operating at a coefficient of performance of 3 against the same grid intensity emits roughly a fifth of what a gas boiler emits per kilowatt-hour of heat delivered. As the grid intensity falls toward the 20-gram floor under the 2030 commitment, both ratios improve, and electrification becomes the dominant carbon-reduction lever for the household and transport sectors.

Frequency, inertia and the operational floor

Behind the generation mix and the carbon intensity sits the operational integrity layer. The system frequency is held at 50.00 hertz plus or minus 0.2 hertz under Grid Code OC9, with a statutory plus or minus 1 percent envelope (49.5 to 50.5 hertz) under the NESO Transmission Licence, and an automatic Low Frequency Demand Disconnection trigger at 48.8 hertz under the Grid Code. The lightning strike on the Eaton Socon to Wymondley 400 kilovolt transmission circuit at 16:52 BST on 9 August 2019 took the frequency down to 48.8 hertz and triggered 931 megawatts of automatic load shedding across England and Wales for up to 45 minutes; that event reset the operational rulebook on inertia, response and Rate of Change of Frequency.

System inertia has fallen from around 250 gigavolt-amp seconds typical in 2014 to lows of around 70 gigavolt-amp seconds on windy summer Sundays in 2024 as synchronous generation has been displaced by inverter-based wind and solar. NESO lowered the minimum-inertia operational floor in two stages during 2024, from 140 to 130 gigavolt-amp seconds on 28 February 2024 and to 120 gigavolt-amp seconds on 19 June 2024, with a 2025 consultation proposing 100 gigavolt-amp seconds.³ The Stability Pathfinder programme has procured around 12.5 gigavolt-amp seconds in Phase 1 and added 10 contracts worth around 323 million pounds in Phase 2, mainly synchronous condensers and grid-forming batteries. The first grid-forming battery on the Great Britain system connected in Scotland in 2024.

The Demand Flexibility Service moved from emergency-only to in-merit dispatch on 27 November 2024. The annual balancing costs for the 2024 to 2025 year ran at around 2.7 billion pounds, up 10 percent year on year, with Balancing Mechanism accepted volume rising 17 percent to 32.6 terawatt-hours. The Demand Flexibility Service alone delivered 5,421 megawatt-hours of accepted volume across 44 events in the 2024 to 2025 delivery year. The balancing layer is therefore growing in volume and in spend; the operational reform programme inside NESO is the ongoing response to the inertia trajectory and the rise of inverter-based generation across the merit order.