Figure 2: Future cost of EES technologies at 1 TWh cumulative capacity.

Experience curves (dotted lines) are projected forwards to analyse product prices at future amounts of cumulative capacity. In the legend, symbol shape indicates technology scope and colour denotes technology (including application and experience rate with uncertainty). Shaded regions are visual guides indicating the cost reduction trajectory for each application category (at a particular technology scope). These narrow to the price ranges given on the right of the figure: systems used for stationary applications, US$280–400 kWh⁻¹; packs used for transport applications, US$150–200 kWh⁻¹; batteries used for portable applications, US$135 kWh⁻¹. The experience curves outside of these ranges refer to technologies where product prices are reported for a different technology scope (stationary fuel cells and electrolysis: pack-level; lead-acid: module-level). A fuel cell–electrolysis combination that could be used for stationary electrical energy storage would cost US$325 kWh⁻¹ at pack-level (electrolysis: US$100 kWh⁻¹; fuel cell: US$225 kWh⁻¹). kWh_cap, nominal energy storage capacity.