Power density

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

Power density is the amount of power (time rate of energy transfer) per unit volume.[1]

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.

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 material Energy type Specific power (W/kg) Power density (W/m3)
Hydrogen (in star) Stellar fusion 0.00184 276.5
Plutonium Alpha decay 1.94 38,360
Supercapacitors Capacitance up to 15000 Variable
Lithium-Ion Chemical ~250-350 ~700

See also[edit]


  1. ^ Jelley, N. A. (Nicholas Alfred), 1946-. A dictionary of energy science. [Oxford]. ISBN 978-0-19-182627-6. OCLC 970401289.CS1 maint: multiple names: authors list (link)