Question

Give reason In practice unit kWh is used for measuring electric energy , rather than joule

Answer 1

cause it is easy to calculate and accepted everywhere

Answer 2

"For the sake of easy calculation, kilo Watt hour is used for measuring the electrical energy instead of joules. Moreover, joule is the small unit of energy, so it may cause a lot of calculation difficulties to use joule.

As in modern life, we are using so many electrical instruments which consume more electrical energies. So, calculating commercial consumption of the Electrical energy using Joule which is the very smallest unit, will be a difficult task. Thus, kWh is used for these purposes.

We know that, 1 J is the S.I. unit of the Energy. It is related to the Joule  

$1\quad { kWh }\quad =\quad 3.6\quad \times \quad 10^{ 6 }\quad { J }$

$3.6\quad \times \quad 10^{ 6 }\quad { J }$is also called as 1 unit. [Board of the Trade Unit (or B.T.U.)]"