Power density is the amount of power (time rate of energy transfer) per unit volume. It is typically measured in watts per cubic meter (W/m³) and represents how much power is distributed within a given space. In various fields such as physics, engineering, and electronics, power density is used to evaluate the efficiency and performance of devices, systems, or materials by considering how much power they can handle or generate relative to their size or volume.
In energy transformers including batteries, fuel cells, motors, power supply units, etc., power density refers to a volume, where it is often called volume power density, expressed as W/m<sup>3</sup>.
In reciprocating internal combustion engines, power density (power per swept volume or brake horsepower per cubic centimetre) is an important metric, solely based on the internal capacity of the engine, not its external size.
Definition
Power density is commonly defined as the converter’s rated (nominal) output power divided by the physical volume it occupies: Reported values may include or exclude components such as electromagnetic interference (EMI) filters, thermal management hardware (e.g., fans or heatsinks), protective housings or enclosures, connectors, and input or output energy-storage capacitors. Switching converters enables performance beyond the deterministic limits of linear power supplies, whose efficiencies were largely constrained by input-output voltage ratios and a small set of available topologies. This eventually caused high power density to become regarded as a leading benchmark of power-system engineering, being the convergence of efficiency, compactness, and performance in modern power-delivery design.