Why the constraint costs are not painted onto the boundaries
Two questions in this tool cannot be answered from what is published, and both are about geography. Rather than draw a boundary we cannot source, the tool shows what exists and states the gap. This page is the gap.
Constraint cost has no published geography
NESO publishes thermal constraint cost by constraint group, and boundary geometry by boundary name, and no machine readable mapping between the two. The network diagrams that would resolve it are PDFs whose labels do not extract. Joining them by eye would invent a precision that is not published, so the groups and the boundaries are shown side by side and the relationship is stated rather than drawn: SSE-SP and SCOTEX are both Scottish and are the two largest cost groups in every year on record, and 7,654 MW of the 10,229 MW gate 2 storage book sits in Scotland.
What the map paints on the constraints tab instead is the transmission use of system generation tariff, which is the price of constraint rather than its cost, and which does have published geometry for all twenty seven zones. Red is a zone that pays to generate, blue a zone that is paid to.
The connection queue zones have no geometry at all
NESO rations connections against the Clean Power 2030 targets, calculating a permitted capacity per technology per zone. Queue formation allocated all of it, and for battery the remaining figure reads zero in all nineteen zones. The zone areas in the databook are names and approximate descriptions read off a picture on page six; the authoritative shapefiles have never been found. So the zonal screen is a table and not a map, and it stays a table until a boundary file exists.
The one question the published data does not settle
The technical principles state that capacity moved during rebalancing does not endure. A zone that received capacity must fall back below its original ceiling before anyone new can join. A zone that donated capacity has not reached its original ceiling, and new projects can apply there. For battery there were exactly two shifts and no substitutions: T3 donated 457.6 MW to T2, and D5 donated 127.2 MW to D6.
The published remaining table reports zero for T3 and D5 as well. So either it is stated against the adjusted ceiling, in which case 585 MW is contestable now, or against the original ceiling, in which case there is no open door. The two readings differ by the whole answer to whether a new project can apply today. This is the one item in the tool unresolved on the face of the published data, and it is a question for NESO rather than for us.
What is missing from the network drawing
The dashed lines are NESO’s transmission constraint boundaries, the representation the system operator itself uses to manage congestion. The quiet mesh beneath is the grid supply point regions, 362 of them. What is not drawn is the circuits owned by the distribution networks. SP Energy Networks publishes 3,211,536 line assets, National Grid Electricity Transmission publishes its own, and UK Power Networks, Northern Powergrid and Electricity North West all publish 132 kV geometry. Every one of those endpoints returns a 403 to this environment while serving its metadata normally, which reads as a network level block rather than a permissions problem. A browser on an ordinary connection will very likely retrieve what this build could not.
Individual project results from the gate 2 assessment are withheld as commercially sensitive, so a named project cannot be tied to its zonal outcome from the databook alone. Remaining capacity of zero is a statement about permitted capacity under the current methodology, not about physical network capability, and Ofgem and the department opened a review of entry requirements in April 2026, so the figure has a policy half life.