Energy Density vs. Power Density

Easily put, energy density is how much, while power density determines how fast. Energy density is the total amount of energythat can be stored per unit mass or volume (Wh/kg), referring to how long agiven system can run. Power density is the rate at which energy is delivered(W/kg), indicating how quickly energy is discharged. Typically, materials withhigh energy density have low power density, and vice versa.