Revenues in Great Britain rose 74% to £99k/MW/year in September 2026, up from £57k/MW/year in August and 38% above September 2025's £71k/MW/year. That is the highest monthly revenue since December 2022. Wholesale revenues set a new record for the index, and Frequency Response had its best month since October 2025.

Gas averaged £64/MWh, its highest since December 2022, lifting the top of the price curve. At the same time, wind generation rose to 9.2 GW and pulled the bottom of the curve down, with day-ahead prices negative for the first time since July. Day-ahead spreads widened to £122/MWh, 50% wider than August's £81/MWh.

NESO dispatched twice as much battery offer volume as in August. But, for every 1 MWh of battery volume priced below gas that NESO took, it still left more than 10 MWh untaken.

For subscribers to Modo Energy's Research, this article will also cover:

• A breakdown of revenue changes across each service
• Why the widest spreads in over a year came from expensive gas and returning oversupply at once
• Why Frequency Response prices reached their highest in over a year
• The eleven batteries that joined the ME BESS GB index in September
• A data download of all charts

Wholesale revenues drove a record month

Wholesale revenues reached £68k/MW/year in September, £27k above August and the highest monthly figure on record for the ME BESS GB index. The previous high was £48k/MW/year in September 2021.

Driven by higher wholesale spreads, Frequency Response reached £28k/MW/year, £12k more than August. The Balancing Mechanism recovered £8k but stayed negative, at -£8k/MW/year. Offer volume doubled, but batteries still spent more charging on Balancing Mechanism bids than they earned from offers. Imbalance fell £5k to £2k/MW/year, though the figure is likely to rise slightly once further settlement runs are calculated. Reserve and the Capacity Market barely moved, at £3k and £6k/MW/year.

Batteries kept trading between the Balancing Mechanism and the wholesale market, as they did in July and August. In this trade, a battery charges when NESO accepts its Balancing Mechanism bid, then sells that energy in the wholesale market. The cost of the energy shows up as negative Balancing Mechanism revenue, and the sale shows up as wholesale revenue. We looked at how batteries ran this trade in July.

Scottish assets did a lot of this trade in September. Roaring Hill, Jamesfield 1, Jamesfield 2 and Blackhillock 1 charged in the Balancing Mechanism and discharged in the wholesale market. As a result, each earned between £140k and £146k/MW/year in revenues, against £104k/MW/year for the two-hour index.

Hyde topped the two-hour ranking at £148k/MW/year excluding the Capacity Market, almost entirely from wholesale. All ten of the top earners beat the two-hour index of £104k/MW/year by at least £32k.

Wholesale Market revenues

Day-ahead spreads reached £122/MWh, the widest in over a year

Average daily day-ahead spreads widened to £122/MWh in September, up from £81/MWh in August, with intraday spreads at £141/MWh. Both are the widest of the past thirteen months, and the day-ahead spread is £45/MWh wider than in September 2025.