By the end of 5 November 2026, the GC0166 deadline, 184 of 196 operational GB battery BM units were submitting Maximum Delivery Offer (MDO) and Maximum Delivery Bid (MDB) data to the NESO control room. That is 7.7 of 8.5 GW. In the Balancing Mechanism (BM), batteries submitting MDO and MDB received 71% more offer volume and 23% more bid volume per MW than batteries that were not, even though each instruction was held for about two minutes less.

The new data has not fixed skip rates: the higher volumes of BESS being taken in the Balancing Mechanism have not kept pace with the new capacity in the fleet. NESO dispatched 7% of in-merit battery offer volume in October, half the rate of a year earlier.

Key takeaways

• Almost all GB battery capacity now sends MDO and MDB to the control room, after a late rush ahead of the 5 November GC0166 deadline.
• Batteries submitting MDO and MDB have had shorter BM instructions, but more of them, and more volume per MW.
• Skip rates remain high. NESO is accepting a smaller share of in-merit battery volume than a year ago, as the fleet grows faster than volume of battery BM dispatches.
• MDO and MDB show the control room how much energy batteries have at any one time. On a windy day, Scottish batteries sat close to full while English batteries cycled on the demand side of the constraint.

Skip rates are costing batteries and consumers

Batteries were dispatched for 427 GWh in the Balancing Mechanism (BM) in October, the most in 13 months. But in-merit battery volume grew faster, so skip rates kept rising. The offer dispatch rate fell from 15% in October 2025 to 7% in October 2026, and the bid rate from 21% to 11%.

This matters both for battery owners, who cannot capture the BM revenue their assets should achieve, and for consumers, through higher balancing costs.

In October, for every 1 MWh of battery offers priced below gas that NESO accepted, it left 11 MWh untaken. Skipped battery offers usually mean gas runs instead. Each skipped battery bid means less curtailed wind is absorbed.

Most battery dispatches last under 10 minutes

From January to October 2026, 75% of accepted battery offer energy and 64% of bid energy came from BM instructions held for 10 minutes or less. Weighted by energy, offers were held for 8.3 minutes and bids for 11.7 minutes on average.

The longer holds are system-flagged bids, mostly for constraint management in Scotland. 18% of bid energy was held for more than 25 minutes, with a spike at 30 minutes. Excluding system-flagged actions, that falls to 1%. In Scotland, 59% of battery bids were system-flagged, against 1% in England.