OpenWindCast

United Kingdom · onshore wind

Great Britain day-ahead wind power forecast

Great Britain has around 14.5 GW of onshore wind capacity, the large majority of it in Scotland. OpenWindCast publishes an independent forecast of GB onshore wind output for tomorrow and scores it every day against NESO's own day-ahead forecast, as published through Elexon.

Record updated 22 Sept 2026 Scored against NESO

Tomorrow · Wed 23 Sept, 11:00 London

Wind power forecast for Wednesday 23 September 2026

3,602MW

24.9% of 14,488 MW installed

NESO, same hour
3,990 MW
Metered
not yet
80% interval
3,011 to 4,397 MW

Most recent scored day, Mon 21 Sept

Metered 2,076 MW. OpenWindCast 1,924 MW, off by 1.1% of capacity; NESO 2,860 MW, off by 5.4%. OpenWindCast closer

Scoreboard against NESO

Live since 8 Jul 2026 · 74 scored days · 8 Jul to 21 Sept

25% lower error than NESO's own day-ahead forecast

OpenWindCast

3.27%

of capacity

NESO

4.35%

of capacity

Closer on

61%

of days

Error is the average miss at the 11:00 target, as a share of installed capacity (nMAE). Back-test before go-live, shown apart: 319 days, 32% lower error than NESO. Only live days count above.

Forecast against the operator and the metered output

One point per day at 11:00, in MW. The shaded area is what the fleet actually produced; before the Live marker the forecast line is the back-test.

Accuracy by type of day

Live record, split by how windy the day turned out. Average error in % of capacity; further left is better.

OpenWindCast NESO
0%2%4%6%8%Low-wind days (33 days)Moderate days (21 days)High-wind days (20 days)0%2.5%5%7.5%Low-windModerateHigh-wind
Type of dayDaysOpenWindCastNESOCloser on
Low-wind days below 15% of capacity332.48%2.82%58%
Moderate days 15% to 35% of capacity213.19%4.17%62%
High-wind days above 35% of capacity204.67%7.07%65%

The daily record

One row per day at 11:00, in MW. Misses are in % of capacity. Losing days stay in the record.

JSON
Day (11:00) OpenWindCast NESO Metered Our miss NESO miss Closer
Wed 23 Sept 3,602 3,990 not yet – – pending
Tue 22 Sept 2,409 2,456 not yet – – pending
Mon 21 Sept 1,924 2,860 2,076 1.1% 5.4% OpenWindCast
Sun 20 Sept 7,340 9,084 7,043 2.1% 14.1% OpenWindCast
Sat 19 Sept 8,857 11,647 8,767 0.6% 19.9% OpenWindCast
Fri 18 Sept 6,156 8,533 3,098 21.1% 37.5% OpenWindCast
Thu 17 Sept 7,655 9,191 7,847 1.3% 9.3% OpenWindCast
Wed 16 Sept 1,991 1,672 1,739 1.7% 0.5% NESO
Tue 15 Sept 5,445 5,239 6,224 5.4% 6.8% OpenWindCast
Mon 14 Sept 3,266 3,751 2,990 1.9% 5.3% OpenWindCast
Sun 13 Sept 419 772 569 1.0% 1.4% OpenWindCast
Sat 12 Sept 7,548 9,777 8,406 5.9% 9.5% OpenWindCast
Fri 11 Sept 3,634 3,513 3,264 2.6% 1.7% NESO
Thu 10 Sept 6,120 7,986 6,960 5.8% 7.1% OpenWindCast

NESO's forecast is captured on the day it is published and held fixed. Operators refine their forecasts nearer to delivery, so a value published later may differ. The most recent day or two settle once measured generation is published.

Forecasting wind in Great Britain

Great Britain has one of the largest onshore wind fleets in Europe, with most capacity in Scotland. The forecast covers GB onshore wind and is scored against NESO's own forecast, published through Elexon.

The GB onshore fleet is unusually concentrated. A large share of it sits in Scotland, much of that in upland terrain across the Southern Uplands and the Highlands. Concentration works against the error cancellation that a country-wide fleet enjoys, so a single weather system arriving at the wrong hour moves a large part of the national total at once. Upland siting also brings the general problem of complex terrain, where the wind at a turbine on high ground can differ substantially from the average a weather model reports for the surrounding area.

The benchmark

The benchmark is NESO's own onshore wind forecast, published through the Elexon BMRS Insights platform along with the metered generation and installed capacity used to score it. Great Britain is the one zone in the portfolio taken from a national platform rather than through ENTSO-E, because Elexon carries the onshore and offshore split. NESO publishes late in the afternoon, so the benchmark for a delivery day is captured that same evening and then frozen.

What is published for Great Britain

One value per day: onshore wind output at 11:00 local time tomorrow, as a load factor and in megawatts. Once NESO's own forecast for that day is published it is captured and held fixed, and once the metered output is settled both forecasts are scored against it. Every day is added to the record above and nothing is removed or rewritten later. How this is measured.

Questions about wind in Great Britain

Is offshore wind included in the GB numbers?

No. This is onshore GB wind only. Elexon publishes the onshore and offshore split, which is what makes an onshore comparison possible for Great Britain.

When is the forecast made?

On the day before delivery. It forecasts GB onshore output at 11:00 London time on the next day, and it is scored once the measured output for that hour is published.

Other bidding zones

Compare every operator: how accurate are European TSO wind power forecasts? · How the scoring works