Energy dataLast updated: Latest settled day 2026-08-06

Wind Curtailment and Constraint Payments

Contents

Two things get said about British wind power, usually by the same people on the same day. The first is that it is the cheapest electricity the country can make. The second is that we pay wind farms to switch off. Both are true, and almost nothing published for a general reader puts the actual numbers next to each other.

This page does that, for one settled day at a time, using the electricity market’s own settlement data. It shows what was paid to turn generation down, what was paid to turn other generation up on the same day, and which fuels were on each side.

What curtailment actually is

Britain’s wind is mostly in Scotland and the North Sea. Its demand is mostly in England. The transmission lines between them can only carry so much, and when the wind is strong the queue at that boundary is longer than the road.

When that happens the system operator cannot simply let the wind farms run. It buys its way out: it accepts offers from generators north of the constraint to reduce output, and offers from generators south of it to increase output, so that supply still equals demand on both sides of a wire that cannot carry the difference. Both sets of instructions cost money and both are published.

The word for the reduction is curtailment. The words for the money are constraint payments, and the two are not quite synonyms — a generator can also be asked to move for ordinary balancing reasons, with nothing congested about it. The tables below keep the two apart.

What one settled day looks like

Settlement figures arrive a day or two after the event and are revised for several days after that, so this is the most recent day that has settled rather than today.

One settled day: 6 August 2026

Two payments, in opposite directions, on the same day. They are set out separately because they are separate money going to separate generators, and adding them together produces a figure smaller than either.

Paid to turn wind down: £794kfor 23,635.9 MWh of electricity wind farms were instructed not to generate, across 70 generating units.
Paid to turn gas up: £8.33mfor 45,397 MWh of extra generation from gas plant, instructed on the same day.

Settlement vintage 2026-08-07T23:14:37+00:00. Elexon revises these figures for several days after the settlement date, so they are provisional until that stops moving.

Why somebody is paid at both ends

The two figures above are not a cost and an offset. They are two separate payments to two separate sets of companies, arising from the same congested wire.

A wind farm asked to stop is giving up revenue it had already sold, so it is paid to do so. A gas station asked to start is burning fuel it had not planned to buy, so it is also paid. Meanwhile some conventional plant asked to reduce output hands money back, because it no longer has to buy the fuel — which is why several payment figures in the tables below are negative, and why the negative sign is the most informative thing in the column.

Adding all of that into one number is the single most common way this subject is reported wrongly. The total is smaller than what wind was paid, and it invites the reader to think the smaller figure is the amount that went to wind farms. Nothing on this page produces such a total, and the database behind it has no column that could hold one.

The question underneath it — what do constraints cost me?— does have an answer, and it is a published one rather than one we derive. The system operator reports what it spends balancing the system, and grid balancing costs tracks that figure day by day. It is the published cost of every balancing action taken, which is a wider thing than curtailment and a different thing from the table below: it is not these rows added together, and nothing here should be read as a share of it.

Every fuel, and why there is no total

One more label needs explaining before the table. A large share of accepted actions come from units that declare no fuel type to the market at all — that group holds most batteries and most aggregated demand portfolios. They appear as not classified by Elexonrather than being dropped, because dropping them would turn the totals into a fact about Elexon’s paperwork rather than about the system.

Every fuel on 6 August 2026

A negative payment is money the generator handed back for being allowed to stop. That is what conventional plant usually does and what wind usually does not, which is the asymmetry the whole argument about curtailment turns on. There is no total row here on purpose.

Balancing mechanism turn-down and turn-up by fuel, latest settled day
Fuel	Turned down	Paid for turning down	Turned up	Paid for turning up	System-flagged actions
Wind	23,635.9 MWh	£794k	33.5 MWh	£0	547 of 581 (94%)
Pumped storage	7,305.6 MWh	£22k	1,909.7 MWh	£328k	112 of 263 (43%)
Not classified by Elexon	5,025 MWh	−£390k	727 MWh	£112k	29 of 5,479 (1%)
Other	3,597.2 MWh	−£235k	303.7 MWh	£44k	21 of 2,181 (1%)
Hydro	2,593.2 MWh	−£116k	4.5 MWh	£414	178 of 195 (91%)
Biomass	1,940.2 MWh	−£30k	0 MWh	£5	11 of 21 (52%)
Gas	1,666.2 MWh	−£137k	45,397 MWh	£8.33m	112 of 492 (23%)

Across all fuels that day: 45,763.4 MWh instructed down and 48,375.3 MWh instructed up, from 9,212 accepted instructions. Volumes in one direction are summed; payments are not.

The days we hold, added up

2 settled days of history, within a window of 30 days. Every stored day reconciled against Elexon’s own settlement stack.

Balancing mechanism turn-down and turn-up by fuel, over the window held
Fuel	Turned down	Paid for turning down	Turned up	Paid for turning up	System-flagged actions
Wind	65,897.4 MWh	£2.64m	33.5 MWh	£0	1,331 of 1,585 (84%)
Pumped storage	12,021.6 MWh	£17k	2,494.2 MWh	£430k	179 of 421 (43%)
Not classified by Elexon	10,572.8 MWh	−£592k	3,541.9 MWh	£620k	90 of 12,495 (1%)
Other	8,807.6 MWh	−£447k	956.3 MWh	£147k	175 of 4,942 (4%)
Gas	5,732 MWh	−£468k	99,038.3 MWh	£18.33m	269 of 1,154 (23%)
Hydro	4,053 MWh	−£142k	4.5 MWh	£414	251 of 280 (90%)
Biomass	2,656.6 MWh	−£74k	0 MWh	£5	11 of 44 (25%)

What this costs a household

Not a line on your bill. The system operator recovers what it spends balancing the system through a charge on suppliers, and suppliers build that into the prices they set. It reaches a household the way network costs and policy costs do: inside the unit rate and the standing charge, spread across everybody.

If you want to see where those components sit in a capped bill, the price cap page breaks the cap into its cost lines, and grid balancing costs tracks the whole balancing bill month by month rather than one day’s actions.

What these figures cannot tell you

What these numbers are, exactly

Instructions, not measurements: Every row is an accepted instruction from the system operator, stored with the status accepted_instruction. It is what a generator was told to do, not a meter reading of what it did, and it must never be placed on the same axis as generation output.
Measured against a declared position: The volume basis is accepted_bid_volume_against_declared_position: the difference between the instruction and the generator’s own final notification of what it intended to produce. The wind that was actually blowing does not enter into it.
Not every accepted bid is a constraint: A wind farm can bid to come off for ordinary energy-balancing reasons as well as because the network is congested. The tables show how many of each fuel’s accepted actions the system operator flagged as taken for system reasons, so the two are never presented as one.
Great Britain: The balancing mechanism covers England, Scotland and Wales. Northern Ireland is on the all-island market and is not in these figures.

Whether it was worth it. A constraint payment buys something real: the network stays inside its physical limits and the lights stay on. Whether the cheaper answer is more transmission, more storage, or building generation closer to demand is a genuine argument, and no figure here settles it.

What a particular wind farm earned.These are daily totals by fuel category. The underlying data is per generating unit and per instruction, and it is aggregated before it is stored — a day is tens of thousands of rows, none of it readable by anybody who does not already work in the market.

What happened today. Settlement lags the event and then gets revised. A figure on this page is provisional until the settlement vintage beside it stops moving.

Source and scope

Elexon Limited balancing mechanism settlement data: accepted bid-offer acceptances, the settled volumes beneath them and the cashflows that settle them, aggregated to one row per settlement day per fuel category before storage. Great Britain. Contains BMRS data © Elexon Limited copyright and database right {year}.

Read the methodology.

Frequently asked questions

What is wind curtailment?

It is the electricity system operator instructing a wind farm to generate less than it could. It usually happens because the network cannot carry the power from where it is being made to where it is needed — most often across the boundary between Scotland and England — so generation on the far side has to come down and generation on the near side has to go up.

Why do wind farms get paid to switch off?

Because they are being asked to stop selling electricity they had already contracted to sell. Generators offer a price at which they will reduce output, the system operator accepts the ones it needs, and the accepted price is what gets paid. The same auction works in the other direction: plant asked to generate more is paid to do so.

Is curtailment the same as a constraint payment?

Nearly, and the difference matters. A constraint payment is one taken because the network is congested. A generator can also be asked to reduce output for ordinary supply-and-demand balancing. The system operator flags which of its actions were taken for system reasons, and the tables on this page show how many of each fuel’s accepted actions carried that flag.

Do I pay for curtailment on my bill?

Indirectly. The system operator recovers what it spends balancing the system through a charge on suppliers called BSUoS, which suppliers include in what they charge customers. It is not a separate line on a domestic bill and no household is billed for a particular payment to a particular wind farm.

Does curtailment mean the electricity was wasted?

The energy was not generated, so nothing was thrown away in the physical sense, but the opportunity was lost — cheap, low-carbon output that could have displaced something else did not happen, and money changed hands. That is what makes the case for more transmission capacity and for storage, and it is also why the figures are worth publishing rather than arguing about in the abstract.

Are these figures the same as how much wind generated?

No, and they must never be read as such. Every figure here is an accepted instruction measured against what the generator itself said it intended to produce, which is a declared position rather than a meter reading. They cannot be added to, subtracted from or charted beside the generation figures on our live electricity page.