Wind, exports and free hours

Where the data comes from

• Prices: N2EX day-ahead hourly wholesale prices for GB, the same prices FPRates uses to work out FreePhase rates and free hours.
• Generation and interconnectors: Elexon's half-hourly generation by fuel type, which includes every interconnector separately, with exports shown as negative.
• Solar and total wind: NESO's historic generation mix, which includes embedded (local) wind and solar that Elexon's figures don't.

1. Wind lowers the price, but not to zero

Daily averages for September 2026, windiest and calmest days. Wind here is the total of transmission and embedded wind.

The five windiest days averaged about £92/MWh, against about £178/MWh for the four calmest. Wind roughly halves the price. But days with 17–18 GW of wind still came in at £95–£125, and gas never dropped below about 3,500 MW. Only 19 September got near zero.

2. On windy days, Britain exports

Average net flow over all interconnectors (Norway, France, Belgium, the Netherlands, Denmark and Ireland). Negative means exporting.

Every windy day was a net export day, and the calm day was a heavy import day: a swing of up to about 5,400 MW. On the calm day Britain drew 1,400 MW of Norwegian hydro flat out. On the windiest day it sent wind the other way.

This is the market working as designed: power flows to wherever it is worth more. With European prices held up by expensive gas, spare British wind is sold abroad, and British prices stay linked to European ones. Only on 19 September, when several cables were exporting at or near their limit for long stretches, did the surplus have nowhere left to go, and the price fell.

3. Two kinds of free hour

Between 1 May and 4 October there were 60 hours with a wholesale price at or below zero, on nine days. Looked at hour by hour, they fall into two groups.

Solar plus wind (most of them)

7 and 13 June, 2, 4 and 25 July, and 5 and 6 September, always around midday (roughly 10:00–16:00 UK time). Typically:

• solar of 7,000–13,000 MW plus wind of 9,000–12,000 MW
• gas pushed down to its minimum, about 1,500–3,000 MW
• Britain usually still importing from the continent

That last point matters. Power flows from cheaper to dearer, so importing at a zero price means Europe's prices were even lower. These were days when all of north-west Europe had more solar than it could use.

Wind alone (once)

The early hours of 19 September, roughly 04:00–08:00 UK time, with no solar:

• transmission wind of about 16,000 MW
• Britain exporting about 5,000 MW to the continent, close to everything the cables could carry
• price just below zero (−£0.90 to −£1.40/MWh)

It took wind strong enough to fill the export cables before the price reached zero. Wind of 11,000–12,000 MW, common on a breezy day, never produced a free hour without help from the sun. (Later on 19 and 20 September strong wind and daytime solar together gave more free hours, again while Britain was exporting.)

4. Gas never switches off

Even in the windiest and sunniest hours, gas-fired generation (CCGT) never fell much below 1,500 MW. Some gas runs for grid stability and to cover places the wind can't reach, especially when Scottish wind exceeds what the cables south can carry. When gas is running, it often sets the price. That's a big part of why windy days stay expensive while gas itself is expensive.

What this means for winter

• Solar largely goes, and with it the main source of free hours over the summer.
• Windy days will still lower prices, but on this evidence they need to be exceptional, roughly enough to fill the export cables to Europe, before prices reach zero.
• Demand is higher in winter, so it takes even more wind to create a surplus.
• While gas is expensive (industry analysts point to the conflict in the Middle East as a major reason), the price on ordinary days stays high, and spare British wind will keep flowing to Europe.

Caveats

• The wind-only free hours come from one night. The ~16,000 MW figure is a first estimate, not a rule. FPRates is now collecting this data daily, and winter storms will show whether it holds.
• Elexon's wind figures cover transmission-connected wind only. The September daily table uses NESO's totals, which include embedded wind, so the two sets of wind figures differ.
• NESO solar data was missing for 6 September.
• This page explains what happened. It is not advice on which tariff to choose.