Watt Hours per Kilogram

What are Watt-hours per kilogram?

The Watt-hour per kilogram is the reference unit used to measure or indicate the density of energy contained or storable in a body. Its abbreviated form is .

The Watt-hours per kilogram express the as a function of the mass of the body: it is then called mass .

In the same way, it is possible to formulate the according to the volume of the body taken into account: in this case, the is said to be volumetric. The unit used here is the Watt-hour per cubic meter, abbreviated as Wh/m3.


The specifics of Watt-hours per kilogram

The Watt-hour per kilogram () comes in several variants depending on the magnitude of the taken into account:

  • 1 Kilowatt hour per kilogram (kWh/kg) then corresponds to 1000 Wh/kg ;
  • 1 Megawatt hour per kilogram (/kg) is equivalent to 1000 kWh/kg or 1 million Wh/kg ;
  • 1 per kilogram (/kg) is 1000 /kg or 1 million kWh/kg.


Examples and practical application

The mass is an important data in energy production and .

The unit Watt-hour per kilogram is widely used in the transportation industry to evaluate the energy contained in a fuel or that can be stored in a battery.


Watt-hours per kilogram in figures

The mass is very variable depending on the material.

Thus, the mass is rather expressed in for:

  • capacitors (1 ) and super-capacitors (27.7 ) ;
  • alkaline batteries (163 );
  • Lithium batteries (500 ).

The kWh/kg is used more for:

  • solid energy sources such as wood (4.5 kWh/kg) and coal (6.6 kWh/kg) ;
  • fuels such as kerosene (11.9 kWh/kg), gasoline (13.1 kWh/kg) and diesel (12.6 kWh/kg).

At the nuclear scale, it is more appropriate to use /kg, with for example:

  • uranium-235 (22 /kg) ;
  • plutonium-239 (23.2 /kg)
  • tritium (93.7 /kg).


Regulatory framework

Not applicable.