Power density

Power density is the amount of power (time rate of energy transfer) per unit volume.

Power density
SI unitW/m3
In SI base unitskg·m−1s−3
Derivations from
other quantities

In energy transformers including batteries, fuel cells, motors, etc., and also power supply units or similar, power density refers to a volume. It is then also called volume power density, which is expressed as W/m3.

Volume power density is sometimes an important consideration where space is constrained.

In reciprocating internal combustion engines, power density—power per swept volume or brake horsepower per cubic centimeter —is an important metric. This is based on the internal capacity of the engine, not its external size.


Storage materialEnergy typeSpecific power (W/kg)Power density (W/m3)
Hydrogen (in star)Stellar fusion0.00184276.5
PlutoniumAlpha decay1.9438,360
Supercapacitors Capacitance up to 15000 Variable
Lithium-Ion Chemical ~250-350 ~700

See also


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