Battery cycling in Great Britain looks like it is slowing down. Across the fleet, average daily cycles have fallen around 15% since the start of 2025. That average masks a split inside the fleet.

The fleet has split in two. One-hour batteries now cycle around 0.6 times a day, down from roughly 1.0 in late 2024. Two-hour batteries have held near one cycle a day, and lately edged higher. The difference is linked to how these assets operate in frequency response. One-hour batteries lean on it for availability income and trade little around it. Two-hour batteries pair it with wholesale and re-trade heavily, on a grid that now spends more time away from 50 Hz.

Key takeaways

• One-hour BESS cycling averages 0.6 times a day, down from roughly 1.0 in 18 months. Two-hour batteries hold near 1.0 and are not falling.
• Two-hour batteries re-trade their positions far more than one-hour systems. They reverse around 0.73 cycles a day of energy on top of steady physical throughput, versus 0.3 for one-hour units.
• Re-trading between frequency response and wholesale has grown about 147% in two years, from 19 to 47 GWh a month, now the second-largest reversal flow after the Balancing Mechanism.
• The grid sits inside its tight 50 Hz deadband just 4.9% of the time in 2026, down from 12.3% in 2020. A fixed frequency response contract now delivers up to 27% more energy.
• Most of the fleet sits well below its cycling limits. The typical two-hour battery runs about one cycle a day against a warranty allowance near two, while the busiest now approach 1.8.

One-hour battery cycling is declining

Two years of daily data, smoothed to a 30-day rolling average, show the cycling of one-hour and two-hour batteries heading in opposite directions.

One-hour cycling fell from 1.0 cycle a day in late 2024 to about 0.6 by May 2026. Two-hour cycling remains around 0.9 to 1.0, and has been a touch higher in recent months.

A single fleet average blends these two trends into a 15% decline. The averages move because the composition of each fleet is changing, which is clearest in the spread across individual assets.

One-hour battery cycling is compressing

Per-asset cycling, compared across the first halves of 2025 and 2026, shows the one-hour distribution compressing. Median cycles dropped from 0.85 to 0.71, and the highest cycling assets now cycle 20% less. All while the number of one-hour units online barely changed.

No new high-cycling one-hour batteries are arriving to lift the top of the range. The one-hour fleet is old, and getting older: the lowest-cycling one-hour assets average around 5.5 years in service, and the oldest go back to 2017, around nine years.