Electrical energy can refer to several
closely related things. It can mean:
* the energy stored in an electric field
* the potential energy of a charged particle in an electric
field
* the energy provided by electricity
In any of these cases, the SI unit of
electrical energy is the joule. The unit used by many
electrical utility companies is the watt-hour (Wh), which
is the amount of energy used by a one-watt load, such
as a tiny light bulb, drawing power for one hour. The
kilowatt-hour (kWh), which is 1,000 times larger than
a watt-hour, is a useful size for measuring the energy
use of households and small businesses and also for the
production of energy by small power plants. A typical
house uses several hundred kilowatt-hours per month. The
megawatt-hour (MWh), which is 1,000 times larger than
the kilowatt-hour, is used for measuring the energy output
of large power plants.
The terms "electrical energy"
and "electric power" are frequently used interchangeably.
However, in physics, and electrical engineering, "energy"
and "power" have different meanings. Power is
energy per unit time. The SI unit of power and electricity
is the watt. One watt is a joule per second. In other
words, the phrases "flow of power," and "consume
a quantity of electric power" are both incorrect
and should be changed to "flow of energy" and
"consume a quantity of electrical energy."
