​Battery energy storage revenues in Great Britain fell to £47k/MW/year in December, down 19% from £59k/MW/year in November. This marks the lowest monthly performance of 2025 and a 45% year-on-year reduction from December 2024.

The timing of cold weather and low wind generation explains the contrast. In December 2024, low wind and high demand coincided, pushing revenues to £86k/MW/year. In 2025, similar conditions arrived after Christmas when demand had already collapsed.

This pattern echoes December 2023, when batteries hit all-time revenue lows as mild weather and high wind suppressed prices over the holiday period. It highlights how December remains the most volatile month for BESS revenues, and outcomes depend heavily on when tight conditions arrive.

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

• A breakdown of revenue changes across each service
• Why the Christmas demand reduction hit revenues so hard
• Balancing Mechanism dispatch dynamics and CCGT competition
• A data download of all charts

Frequency response drives revenues to 2025 low

Batteries in Great Britain earned £47k/MW/year in December, their lowest level since July 2024 when the ME BESS GB Index hit £39k/MW/year. Year-on-year, December 2025 revenues fell 45% compared to December 2024. Every revenue stream declined, as the conditions that led to high wholesale prices in 2024 did not materialise in 2025.

Frequency response accounted for three quarters of the revenue decline, falling £8.6k/MW/year. Balancing Mechanism revenues made up most of the rest, dropping £3.2k/MW/year. Wholesale and imbalance revenues provided modest offsets, while Capacity Market revenues increased as winter payments continue.

Batteries were dispatched for record volumes of energy Bids, meaning more batteries imported Balancing Mechanism energy and sold it in wholesale markets. This propped up wholesale revenues despite poor trading conditions, shifting losses to other markets.

Wholesale Markets

Why revenues fell: the Christmas timing problem

December revenues depend on when cold, low-wind weather arrives. In 2025, the timing worked against batteries. Daily revenues averaged £55k/MW/year from December 1st to 20th. After December 21st, they fell 33% to £37k/MW/year. The best trading days came early: December 10th and 19th both delivered £82k/MW/year, while December 14th reached £74k/MW/year.

December 27th was the worst day of the year. Batteries earned just £15k/MW/year as wholesale spreads reached only £24/MWh. Wholesale and Balancing Mechanism revenues both turned negative. Only frequency response and Capacity Market payments kept net revenues above zero.

December 2024 vs December 2025 revenues: timing made the difference

December 2024 marked a rebound in battery revenues, hitting a two-year high. Colder weather and low wind arrived on December 11th and 12th, before the Christmas demand drop. Residual demand hit 37 GW on those days. Prices spiked to £496/MWh, and batteries earned their highest single-day revenues in two years. Since then, gas prices have fallen 40%, suppressing the price peaks typically seen in winter.