In practice the unit kWh is used for the measurement of electrical energy, rather than joule.

Explanation

i Electrical energy = Electrical power `xx` time.
ii. For practical applications, devices consuming high electrical power are used over the period of time.
iii. This leads to heavy expenditure of electrical energy. To measure such value of energy unit joule is significantly small.
iv. Hence, unit kWh is used in practice. Unit 1 kWh represents power of 1 kW used for 1 hour and equals `3.6 xx 10^(6) J`.