In 2023, battery energy storage systems in Great Britain saved 950,000 tonnes of carbon emissions. This year they are on track to increase this by 50%. This means batteries will have saved the equivalent emissions of a car driving from New York to Los Angeles 1.32 million times.
This article covers the total carbon saved by batteries since 2021 and where this carbon saving comes from. If you want to read about how we calculated these figures and the assumptions we made, check out our methodology article.
Batteries have saved 4% of power sector carbon emissions in 2024
The power sector comprises the large-scale production of electricity for industrial, residential, and rural use. In 2023, carbon emissions savings from battery energy storage offset 2.2% of all power sector emissions. This has nearly doubled to 4.1% in 2024, based on data until August 31st.
Carbon savings from batteries as a percentage of power sector emissions also doubled between 2022 and 2023. This comes as battery energy storage capacity has continued to grow, while total power sector emissions have fallen.
Carbon emissions savings from inertia and direct energy actions have increased the most since 2022
Batteries save carbon through three different sources:
- Energy actions - batteries save carbon directly through their energy actions, by importing low-carbon energy and exporting it when demand is high. These are the only savings that come directly from the energy batteries are importing and exporting.
- Frequency response services - They perform dynamic frequency response services, which help keep grid frequency at 50Hz. This means the grid uses fewer carbon-emitting plants for Mandatory Frequency Response (MFR), which has the same purpose.
- Inertia management savings - Batteries provide fast-acting post-fault frequency response which means the grid is less reliant on gas generation to maintain high inertia, which also helps maintain grid frequency.
Batteries providing frequency response reduced carbon emissions by 380,000 tonnes in 2023, and are on track to provide a similar saving in 2024. This figure has grown 12% from 2022.
In contrast, carbon savings directly from battery actions have increased to ten times their 2022 levels. Similarly, savings due to reduced CCGT inertia management have risen from 58,000 tonnes in 2022 to 580,000 in 2024 so far.
Carbon savings from reduced inertia management make up 60% of all savings
Batteries provide their biggest reduction in carbon emissions through inertia management savings. NESO needs to manage grid inertia as it helps frequency remain stable during large outages. However, this requirement has massively reduced since 2022, as NESO has reduced the target grid inertia from 140 GVAs to 120 GVAs. According to NESO, 30% of this can be attributed to batteries that perform Dynamic Containment.
Batteries and renewable generation essentially share carbon savings from reduced inertia. Batteries help the grid remain stable at low inertia, but renewable generation lowers inertia in the first place.
This shift to a lower inertia grid began in 2023, which is why there is such a large increase in inertia emissions savings after 2022. These savings are set to increase by 55% from 2023 to 2024.
Battery wholesale activity has the largest impact on direct emissions savings
Another way that batteries reduce emissions is through energy actions. They do this on a daily basis, and we can see an example of this on April 15th, 2024, when batteries saved over 1,000 tonnes of CO2. They did this by importing wholesale energy when the marginal carbon intensity (shown in red on the chart) was low.
Marginal carbon intensity is different to the average carbon intensity reported by NESO. It represents the carbon intensity of the marginally priced power plant. i.e. the power plant that would replace the batteries if they weren’t exporting power. If you want to know how we calculate this, you can read our methodology article.
This means batteries were importing zero-carbon renewable energy. Later in the day they exported this zero-carbon energy when the marginal carbon intensity was high. If batteries weren’t providing this energy, another generator would need to, and this would be at the higher marginal carbon intensity, increasing carbon emissions.
Batteries import power when carbon intensity is low and export power when it is high because they respond to price signals in the market. Wholesale prices and carbon intensity are linked as they are both influenced by the volume of renewable generation online.
The timing of frequency response actions doesn’t correspond to the grid's carbon intensity. This is because they respond to grid frequency, which is not influenced by renewable generation. This means they have minimal impact on carbon emissions saved directly from battery energy actions.
Increased wholesale trading has led to lower carbon emissions
Between 2022 and 2023, batteries shifted their focus from frequency response services to wholesale trading. This is because installed battery volume grew faster than frequency response volume requirements. As a result, the volume of batteries available in the wholesale market doubled between 2022 and 2023.
Due to the link between wholesale trading and reduced carbon emissions, total carbon savings directly from battery actions have increased since the end of 2022. The energy exported from batteries participating in frequency response services caused 36,000 tonnes of carbon emissions in 2024. However, this is offset by the 102,000 tonnes of carbon saved by batteries through wholesale trading. Overall, batteries saved 56,000 tonnes of CO2 in 2024 directly from energy actions.
Dynamic Containment Low has the largest MFR carbon benefit
NESO manages the grid's frequency in several ways. One is through dynamic frequency response services, which are dominated by batteries. Another is Mandatory Frequency Response, which is provided by carbon-emitting CCGTs. Batteries providing frequency response reduce the need for CCGTs to do so. Therefore, every MW of frequency response provided by batteries has an associated carbon emissions saving or cost.
Carbon costs come from batteries performing high-frequency response services. This means they are reducing their energy output rather than CCGTs doing so. Carbon emissions savings come from batteries performing frequency response low, which means batteries increase their energy output instead of CCGTs. These will be referred to as ‘MFR Delivery savings’. Additionally, batteries providing frequency response allow CCGTs to run more efficiently, resulting in an ‘MFR Efficiency saving’.
For more details on this element of battery carbon savings, read our methodology article.
Different frequency response services performed by batteries also have varying impacts on the volume of MFR required. As a result, the most carbon-saving service is Dynamic Containment Low, which saves 72kgCO2/MW.
MFR delivery savings have reduced as batteries provide more High frequency response
While frequency response Low services save carbon due to higher CCGT efficiency, High services do not have an efficiency cost. Frequency response High services have increased in volume since 2022 by more than frequency response Low services. This means that in 2023 and 2024, carbon savings from MFR efficiency were higher than in 2022, but MFR delivery savings were lower.
Batteries that provide the most Dynamic Containment Low save the most carbon
Richborough Energy Park 2, optimized by Shell and owned by Sosteneo, has saved 13,000 tonnes of carbon in 2024 so far, more than any other battery. 94% of this came from reduced Mandatory Frequency Response emissions.