Question

In what unit does the electric meter in a house measure the electrical energy consumed? What is its S.I unit?

Answer 1

An electric meter measures the electrical energy consumption in billing cycles, which are measured in kilowatt-hour (kWh).
One kilowatt-hour is equivalent to energy consumed by $1kW$ appliance in one hour.
Since $1Watt=1J{s}^{-1}$
$1kWh=1kW\times 1hour$
$=1000\frac{J}{s}\times 3600s$
$1kWh=3.6\times {10}^{6}J$
The S.I unit of electrical energy consumed is joule (J) .