​Britain's battery fleet saved 824,000 tonnes of CO₂ in 2025 - 43% more than in 2024 (with an updated methodology). That's equivalent to taking 366,000 petrol cars off the road for a year. At an average UK Emissions Trading Scheme carbon price of £49/tonne, batteries offset £40mn worth of emissions, a similar magnitude to the cost savings they deliver through energy balancing.

Frequency response drove the majority, saving 514,000 tonnes — 62% of the total. Wholesale trading saved 164,000 tonnes. Balancing Mechanism dispatches saved 146,000 tonnes.

This year's carbon calculator features an updated methodology, with wholesale and Balancing Mechanism activity separated into two sections using NESO's skip rate data. Previously calculated inertia savings have been removed. For methodology detail on wholesale and frequency response, see the 2024 carbon savings methodology article. Contact the author at zach@modoenergy.com

Carbon savings increase by 43% as Balancing Mechanism activity grows

Carbon savings from batteries increased 43% between 2024 and 2025. Frequency response remains the largest contributor, but the growth is coming from elsewhere.

Since 2023, frequency response savings have grown 35% - broadly in line with the 40% rise in Dynamic Containment Low volumes procured. Wholesale and Balancing Mechanism savings have increased five-fold over the same period. Battery dispatch volumes in the Balancing Mechanism rose from 12 GWh in 2023 to 175 GWh in 2025.