New Long-Duration Storage Scheme: UK Drives Battery Storage with Discharge Durations of up to 18 Hours – Market Trend Already Visible
Copenhagen – The UK is promoting the construction of batteries with long discharge durations through a dedicated long-duration storage scheme. Independent of the British scheme, the trend towards longer discharge durations is already visible in the market. Copenhagen Infrastructure Partners (CIP) is building a four-hour storage system in Scotland, doubling the discharge duration compared with its three previous large-scale storage systems in the region.
Kilmarnock South: CIP Doubles Discharge Duration at New Large-Scale Storage System in Scotland
CIP, through its Copenhagen Infrastructure IV fund, has taken the investment decision for Kilmarnock South in Ayrshire. The lithium-ion storage system has a power capacity of 350 MW and a storage capacity of 1,400 MWh. At full power, the facility can feed electricity into the grid for four hours, and correspondingly longer at reduced power. Construction has begun, and commercial operation is planned for the first quarter of 2028. According to the company, CIP is investing more than EUR 270 million.
This doubles the discharge duration compared with CIP's three other Scottish large-scale storage systems. Coalburn 1, Coalburn 2 and Devilla each have a power capacity of 500 MW and a storage capacity of 1,000 MWh and are designed for two hours. Coalburn 1 has been in operation since August 2026, and Coalburn 2 is due to follow in 2027. Together, the four projects have a power capacity of 1.85 GW and a storage capacity of 4.4 GWh.
With its four-hour discharge duration, Kilmarnock South does not fall under the British LDES Cap and Floor Scheme, which requires a minimum of eight hours. The project is therefore to be viewed independently of the scheme, but it illustrates the existing market trend towards battery storage with longer discharge durations.
One driver of storage expansion is the high share of wind energy in Scotland combined with existing grid constraints. According to the British system operator NESO, 13 percent of possible wind power generation in Great Britain was curtailed in 2024/25. Battery storage can absorb surplus electricity and feed it back into the grid later.
“Well-sited battery energy storage projects provide valuable power system flexibility which enables the full benefits of low-cost renewables to be captured, strengthening security of supply and helping to both cut and stabilise energy bills for consumers,” said Nischal Agarwal, Partner at CIP.
British Battery Storage Market: Discharge Duration and Installed Capacity Rising
Data from Modo Energy show that Kilmarnock South is part of a broader market development. According to the market analyst, the average discharge duration of British battery storage systems rose from 1.33 hours at the end of the third quarter of 2024 to 1.65 hours at the end of the second quarter of 2026. The new CIP storage system, at four hours, is well above that level.
Installed power capacity is also growing. According to Modo Energy's calculations, 7.6 GW of battery storage was in operation at the end of June 2026, compared with 4.5 GW when the British Clean Power 2030 action plan was published in December 2024. For 2030, the government estimates a total requirement of 23 to 27 GW, by which time at least 95 percent of British power generation is to come from low-carbon sources.
Longer discharge durations also broaden the range of applications. Battery storage can shift larger volumes of electricity over longer periods and, for example, bridge longer phases of low wind and solar power generation.
Cap and Floor Instead of CfD: How the UK Is Structuring the Investment Framework for Long-Duration Storage
Through the Long Duration Electricity Storage (LDES) Cap and Floor Scheme, the UK aims to specifically stimulate the deployment of storage with a discharge duration of at least eight hours. A minimum power capacity of 100 MW applies to mature technologies such as lithium-ion batteries and pumped-storage hydropower, while the threshold is 50 MW for less mature technologies.
Unlike the British Contract for Difference (CfD) model for power generation, the scheme does not hedge a single strike price. Instead, the cap and floor model defines a broader revenue corridor for the operator: if eligible revenues fall below the lower limit (floor), consumers pay the difference up to the floor. If revenues exceed the upper limit (cap), the additional income is shared with consumers under the scheme's rules. The model thus limits investors' revenue risk while also giving consumers a share of income above the cap.
The first project selection indicates the scale. On June 26, 2026, Ofgem provisionally selected 16 projects with a total power capacity of 7.6 GW and a storage capacity of 136.9 GWh: eleven lithium-ion battery storage systems, three pumped-storage hydropower plants in northern Scotland, one compressed-air energy storage project and one flow battery project.
Discharge durations range from eight to 32 hours. Lithium-ion storage systems are planned with up to 18 hours. This figure is reached by Field New Deer with 400 MW and Field Rigifa with 200 MW. The three pumped-storage plants have durations of 15 to 32 hours, including Coire Glas with 1,440 MW and 32 hours, and the compressed-air storage project has 30 hours.
However, the provisional selection does not mean that all projects will be realised. According to an analysis by Modo Energy, nine of the 16 projects had a full planning consent at the beginning of September. In sizing the portfolio, Ofgem takes possible project failures into account.
Ofgem intends to decide in autumn 2026 which facilities will ultimately be admitted to the cap and floor regime. The development thus shows two stages of the British storage market: the discharge duration of commercial battery storage is already rising today. At the same time, the UK is creating an investment framework for the next stage, from eight hours upwards, up to lithium-ion projects with 18 hours of discharge duration.
Source: IWR Online, 07 Oct 2026
