Ultracapacitors have several distinct advantages, the first of which is their high energy storage. Ultracapacitors possess energy density that is several times higher than that of traditional capacitors. Compared with batteries, they also possess a low internal resistance (ESR), furthering their high power-density capabilities. Ultracapacitors are also capable of performing at low temperatures. Tecate Group's ultracapacitors, with their use of patented technology, are capable of delivering energy down to -40°C with minimal effect on efficiency. And finally, ultracapacitors have very fast charge and discharge rates. Since they achieve charging and discharging through the absorption and release of ions, high current charging and discharging is possible without any damage to the parts.
Ultracapacitors do have a few limitations. They have low per-cell voltage, typically around 2.7V, which means that any higher-voltage applications require the cells to be connected in series. Also, because of their time constant, ultracapacitors are not suitable for use in AC or high-frequency circuits.