Experience curves for electrical energy storage technologies
The investment cost, or upfront capital cost, is a key determinant of a technology’s competitiveness. It determines whether a novel technology takes off and enters the mainstream, or remains forever stuck in the laboratory and demonstration phase. However, investment costs for new low-carbon technologies are typically higher than those of the incumbents they seek to replace. It is therefore essential to understand the cost-reduction potential of electricity storage technologies.
Figure 1 shows product prices per unit of energy capacity for the most common electricity storage technologies as a function of increasing cumulative installed energy capacity. Experience rates are derived from the slope of experience curves and quantify the percentage change in product price with each doubling of cumulative installed capacity.
All experience rates of the analysed electricity storage technologies are between 10% and 30%, except for pumped hydro systems and lead-acid packs. The highest experience rates can be observed for lithium-ion cells (consumer electronics) and battery packs (EVs). This explains the dominance of the lithium-ion technology in these applications. The strong experience rates in combination with significant deployment levels enabled competitive price levels in the respective applications.
Electricity storage technologies for which there is not enough data are excluded, but these may still hold promise in the future, e.g., flywheels, compressed air, gravity storage.
Figure 1 – Experience curves for storage technologies, measured by energy capacity. Product prices measured in real 2020 USD per nominal energy capacity as a function of cumulative installed nominal energy capacity. The dotted lines represent the resulting experience curves based on linear regression of the data points. The legend indicates product scope (installed system, pack, cell) and technology (including application, experience rate with uncertainty, and years covered by the dataset). Experience rate uncertainty is quantified as its 95% standard error confidence interval. Grey bars indicate overarching trend in cost reduction for technologies relative to technology maturity as a function of cumulative installed capacity: Emerging (<1 GWh), Growing (<100 GWh) and Mature (>100 GWh). Fuel cells and electrolysis must be considered in combination to form a hydrogen-based storage technology (with an assumed energy-to-power ratio of 10). Data for lead acid (pack) refer to multiple applications, including uninterruptable power supply or heavy-duty transportation.
Experience rates reveal the underlying trend in how historical prices have fallen as a function of increasing cumulative deployed capacity. It is possible to project these experience curves forwards to potential future deployment levels. Of course, there is no guarantee that prices will continue to fall at the same rate as they have done in the past; however, this approach does give an objective, evidence-based view on how costs might develop.
Figure 2 shows the experience curves projected forwards to 1 TWh of cumulative capacity. This enables to derive a cost-reduction trajectory that applies to all electricity storage technologies analysed. It implies that all commercially successful technologies have the potential to cost between 100 and 500 USD/kWh once 1 TWh has been deployed. As this applies to all technologies, it means that the technology that manages to bring most capacity to market is likely to reach this range first and be most cost-competitive. Thus, modular technologies that can be used in multiple applications have an advantage (e.g. li-ion).
You can explore the data to make your own investment cost projections at http://www.energystorage.ninja.
Figure 2 – Future cost of storage technologies at 1 TWh cumulative capacity. Experience curves (dotted lines) are projected forwards to 1 TWh cumulative installed energy capacity to analyse potential future product prices. The legend indicates product scope (installed system, pack, cell) and technology (including projected product price at 1 TWh cumulative installed capacity). Shaded region is a visual guide indicating the cost-reduction trajectory across all technologies. These narrow to the price range given on the right of the figure. kWhcap - nominal energy storage capacity.
Schmidt, O., & Staffell, I. Monetizing Energy Storage - A toolkit to assess future cost and value. Oxford University Press. Forthcoming.