Research shows rapid cost reduction of long-duration energy storage

The cost of long-duration storage, or long-duration energy storage (LDES), will drop significantly in the coming years. That's according to the new technical report Cost Benchmarking for Long Duration Energy Storage Solutions., conducted by EPRI in collaboration with the LDES Council. The study shows that various LDES technologies will become on average about 37% cheaper toward 2030, thanks in part to technological development and scale-up of production.

LDES - systems that can store energy for many hours to days - is becoming increasingly important as the share of renewable electricity grows and the demand for reliable, clean energy increases. The need is compounded by the rapid increase in data centers, electrification of industry and the growing impact of prolonged moments of low solar or wind.

Wide variation, but clear cost decrease

Based on cost data from technology developers, EPRI analyzed five categories of LDES technologies. The study contrasts 2025 costs with projected costs in 2030. Some notable findings:

• Intraday electrochemical systems (such as flow batteries) drop to $244-$358/kWh in 2030, with an average cost reduction of ~37%.
• Compressed-gas techniques show decreases of 6-25%.
• Pumped heat energy storage shows a relatively narrow range of $236-$338/kWh in 2030, indicating converging cost structures.
• Multi-day systems (100 hours of storage) drop toward $26-$38/kWh, due to economies of scale with longer durations.
• Thermal storage (TES) shows the greatest spread as well as the largest decrease, with cost reductions of 16-47% toward 2030.

A key insight from the report is that LDES technologies tend to be relatively expensive per kW of power, but actually become competitive over the longer term because the cost per additional kWh stored increases slightly. In doing so, they provide robust solutions for long periods when renewable generation is low.

LDES as a strategic building block for the European energy market

Parallel to the publication, Energy Storage Europe, in which Energy Storage NL is a member, among others, called on European policymakers to explicitly embed LDES in European energy and market design. Other countries are ahead in this effort: California, Australia and the United Kingdom already have specific LDES programs. Europe is called upon to take that step as well.

In a joint letter, they argue that Europe should embrace the deployment of LDES on an accelerated basis to, to this end, they make the following recommendations:

1. Include LDES in system planning and adequacy analyses: LDES is still barely considered in many European plans, so investment decisions are made without considering technology that can handle long-term system stress. This leads to overinvestment in fossil-fuel peaking plants or expensive grid reinforcement. By making LDES a structural part of NECPs (National Energy and Climate Plans) and adequacy analyses, a more realistic picture of system needs emerges and long-term flexibility is taken into account as naturally as solar, wind and short-term batteries.
2. Reform market mechanisms, ancillary services, network rates and taxes: The current market rewards mostly short-term flexibility. As a result, the value of systems that can deliver for several hours to days is not seen. Adjustments are needed because balancing markets now do not focus on long duration, network tariffs do not reflect the system value of LDES, and taxes can even lead to double charging and discharging. Modernizing market and tariff structures creates a level playing field in which LDES can recover its economic value.
3. Align capacity mechanisms with European adequacy methodologies: Capacity markets assess technologies primarily on power (MW), whereas duration (MWh) is crucial for security of supply during prolonged periods of low renewable generation. Better aligning capacity mechanisms with ERAA methodology will allow LDES to compete fairly with fossil backup and focus support on solutions that actually reduce system stress. International examples such as California and the UK show that this accelerates market development.
4. Targeted investment instruments and long-term contracts: LDES requires high initial investments while returns are uncertain. Long-term contracts (such as CfD-like models) reduce financing costs and make projects bankable, especially for seasonal storage. Additionally, specific LDES categories within EU instruments (Innovation Fund, CEF, state aid) help get projects off the ground. Accelerated and clear permitting processes are essential as many storage projects require extensive civil or geotechnical work.