London is a world-tier hub, but a new connection faces historic waits up to 15 years and prohibitive cost (the TMO4+ reform exists because entry stalled). Unlike Northern Virginia, the gate has genuinely stalled new entry, so no up-override; improving as the reform reorders the queue.
NGED publishes demand headroom at Bulk Supply Point and Primary substations for both the existing connected position and the future contracted position, so a candidate site can be checked against a named substation before any application. Equivalent datasets exist for the other GB distribution operators.
How to check for your site: Identify the Bulk Supply Point and Primary substation for the candidate site and read its demand headroom, then confirm with the DNO, since contracted position moves.
Why: NESO's TMO4+ reform is issuing Gate 2 offers and reordering a roughly 96 GW queue toward first-ready-first-connected, targeting historic waits of up to 15 years.
What would change the read: Firm pre-2030 connection offers materialising at scale for new large loads.
For new supply: NESO's first-ready-first-connected reform is issuing Gate 2 offers against a roughly 96 GW queue, so a ready generation project can now advance.
Beyond the grid: Land and water permitting is contested even as access improves: ministers have approved hyperscale sites on green belt land, but a 90 MW Buckinghamshire approval was quashed in 2026 after the government admitted a serious error over power and water concerns, and data centres have now been folded into the centralised NSIP planning regime. Leigh Day The Register
Severe access: historic waits up to 15 years; the TMO4+ 'first ready, first connected' reform (live 2025) is reordering a ~96 GW queue.
Tight availability on a constrained system.
Very high power cost (~$100+).
World-tier momentum (London FLAP-D), but entry is gated.
Cleaner grid (~155 g), wind-heavy (~30% of generation).
Transmission-level Energy Not Supplied was 359 MWh in 2024/25 against a regulated incentive neutral point of 147 MWh, so the operator missed its reliability target by roughly 2.4 times on the measure Ofgem actually holds it to. Average network availability was 99.9998%. For a large load the target miss is the signal: bulk supply is highly available but the trend on the regulated measure moved the wrong way.
What this means: A large new load faces occasional exposure here. Monitor conditions and keep a contingency plan.
measured · National Grid Electricity Transmission RIIO-T2 reliability performance
Average customer interruption (SAIDI) of 39.71 minutes per year in 2024/25, excluding major event days as filed.
measured · Ofgem RIIO-ED2 2024/25 summary
Winter margins are wind-dependent and have been tight in the past, though the 2025/26 base-case margin of 6.1 GW (about 10%) is the strongest since 2019/20, helped by storage, gas availability and the Greenlink interconnector.
What this means: A large new load faces occasional exposure here. Monitor conditions and keep a contingency plan.
assessed · NESO winter 2025/26 margins
Connection terms for large demand are mid-reform and the reform is explicitly retroactive: a second round of queue reordering will change existing connection offers, and distribution-level demand connections are in scope this time. Government is separately consulting on whether very large users such as data centres should be required to provide a mandatory minimum level of demand flexibility, letting the operator curtail them at times of system stress. Treat a GB connection offer as firm today but revisable, and price the possibility of a curtailment obligation you did not choose.
Utility feeds, UPS, storage, on-site generation, islanding, black start and the residual energy you still expect to lose are properties of a specific site design, not of a market. This layer only exists once there is a site, and we never assert it for you.
What this means: The supply crunch looks likely to ease for a new load energizing here in the coming years.
The average customer loses about 39.71 minutes of power per year (2024/25) (reported as Customer Minutes Lost, a SAIDI-equivalent measure). This is the standard regulator outage measure (SAIDI); lower means a more reliable grid.
Source: Ofgem RIIO-ED2 2024/25 summary
283 GW
48 months
The full queue analysis for this market, which covers the share of projects that give up and leave the queue (the withdrawal rate), how much of the queue is data centers, and the sources, is available through /api/v1/queue/great-britain with a paid key. These are generation and storage queue figures: they show interconnection-system congestion, not a typical large-load connection wait.
Low
£27.10 per kW-year
2029/30 (T-4)
Great Britain's four-year-ahead capacity auction cleared at £27.10 per kW-year for 2029/30, less than half the £60 to £65 of the prior two years. The forward cost of firm capacity is falling here, the opposite of PJM.
Source: GB T-4 Capacity Market 2029/30 (Timera Energy). A derived indicator: we publish the public clearing price and our read, never paywalled exchange data.
$118 to $168 per MWh
Midpoint about $138 per MWh
Britain carries one of the highest large-load bands in the coverage: gas-set wholesale prices, a capacity-market charge, and heavy network and policy costs all stack on top of each other. Delivered cost for a large load routinely runs well above the continental average.
This market's band is free here; the ranked cross-market table with every market's precise midpoint is the Analyst Desk. See the ranked view.
Basis: triangulated from public sources, in US dollars per MWh delivered to a large high-load-factor load, excluding refundable taxes. Sources: EU and UK industrial electricity prices (IEA Electricity 2026) · Non-household electricity prices (Eurostat).
High
3 of 4 data layers measured
Full
3 of 3 dimensions: reliability, connection, cost
June 2026
per-layer vintages below
| Layer | Method | Vintage | Freshness | Source |
|---|---|---|---|---|
| PGIQ Rating opinion | opinion | June 2026 | Current | PGIQ methodology |
| Reliability | measured | 2024/25 | Fresh | Ofgem RIIO-ED2 2024/25 summary |
| Forward cost | measured | 2029/30 (T-4) | Fresh | GB T-4 Capacity Market 2029/30 (Timera Energy) |
| Interconnection queue | measured | end-2025 (LBNL 2026) | Fresh | NESO connections reform press release (Dec 2025) |
| Realized cost | triangulated | 2026 | Fresh | EU and UK industrial electricity prices (IEA Electricity 2026) |
Freshness reflects each layer's refresh cadence: reliability annual to three-yearly, capacity-auction and queue yearly, tariffs every year or two. The full cross-market freshness dashboard is at /data-quality.
Not compiled for this market. Identify the serving operator before relying on any figure here, because a market-level read is an average over territories.
Who runs the connection process: National Energy System Operator (system operator), via Connections reform, Gate 2 application. Demand connection terms are mid-reform and the reform reaches existing offers; distribution-level demand is in scope. Where the process starts.
The real-world events that test our Tier 4 call for Great Britain: 2 support it. Each is dated and cited, so you can check the rating against what is actually happening on the ground.
Under the TMO4+ reform, Gate 2 offers for applications up to 2030 are being issued by end-Jun 2026; NESO estimates ~13 GW of firm demand can connect before 2030, with ~86 GW more in 2030 to 2035.
Source: NESO ↗A first-ready, first-connected overhaul targets historic waits of up to 15 years; projects aiming for 2030 should have offers by early 2026.
Source: NESO ↗How Great Britain's reliability-adjusted score and tier have moved, month by month. Part of your Analyst Desk.
This page is our full read on Great Britain alone, and it is free. To decide where a large load should actually go, you need every market side by side, ranked on recurring cost and time-to-connect, with the history and alerts when your shortlist moves. That is the Analyst Desk.
With your Analyst Desk, compare Great Britain against every market side by side, ranked on recurring cost and time-to-connect, with the full history and shortlist alerts.