What batteries do
about the grid gap
New wires take a decade. A battery takes about eighteen months. Here is what that buys, with numbers, and what it does not.
A windy night, as it works today
The wind rises past what the wire can carry. Everything above the yellow line is paid to switch off, and gas plants south of the bottleneck are paid to start in its place. Both payments end up on bills — £410m for the switch-offs alone last year.
The same night with a battery behind the bottleneck
The battery charges on the power that would have been switched off, then discharges in the small hours when the wire has room. Less switching off, less replacement gas. It moves the power in time to when the wire can take it.
The same night with a battery near the city
In the south, the battery discharges through the evening instead of the gas plant that is currently paid to fill the gap. Same wire, less gas, lower bill.
The third job: keeping the grid steady
The grid used to get its stability free from heavy spinning gas and coal plants. As they retire, the system operator pays to keep the grid steady — newer "grid-forming" batteries can supply that too, and are winning contracts in NESO's stability market. That is background for one line on the method page: some gas runs not for energy but for stability, and that cost sits inside the grid-gap bill.
Where batteries stand today
| Operating | 5.0 GW | in the planning database; industry trackers put the real fleet at ~7.2 GW — the database lags |
| Being built | 9.9 GW | |
| Approved, not built | 72.1 GW | 19.4 GW of it approved two years ago or more |
| Refused, last five years | 5.7 GW | see where → |
| In planning now | 42.1 GW |
Approved capacity dwarfs what is built. Some of the queue is speculative and will never be financed — but the bottleneck between approval and operation is connections and delivery, not planning permission. Battery sites appear on the map, coloured by status.
Why they get refused
The recorded reasons are mostly fire safety, landscape, and "not needed here". Fire services have national guidance on battery site safety, and government planning guidance tells applicants to engage fire services early. The numbers on this site say what was refused and where; the merits of each case are for the planning record.
What batteries do not do
They do not replace the wires. A battery shifts power in time, not distance: it cannot move a gigawatt from Caithness to London on a calm week. The wires still need building — batteries cut the bill while that happens.