1 Unit Electricity is the amount of electrical energy consumed by a load of 1 kW power rating in 1 hour. It is basically measurement unit of electrical energy consumption in Joule. 1 kWh (kilo watt hour) and 1 Unit are same. 1 kWh is the amount of energy consumption by 1 kW load in one hour. Therefore, 1 Unit = 1 kWh.
1 Unit Electricity = 1 kWh
= 1 kW x 1 Hour
= 1000 W x 3600 seconds
= 3.6×106 Joule
Therefore, 1 Unit Electricity is equal to 3.6×106 Joule of electrical energy consumption.
You might have seen the electricity bill of your home. The bill amount is based on the cost of 1 Unit Electricity and the number of Units consumed.
Calculation of Power Consumption
Power consumption is basically the energy consumption. Thus, when we talk of power consumption calculation, we basically mean to calculate the energy consumption for a certain time period.
The power consumption of electrical appliances is measured in term of Units. You can easily see the power consumption in kWh in your energy meter. The difference between the two consecutive kWh readings of energy meter taken over a time period gives the number of Units of electrical energy consumed during that period.
Let the initial reading of energy meter at the beginning of month = x kWh
Final reading of energy meter at the end of month = y kWh
Then, total kWh consumed for that month = (y-x)
But 1 Unit = 1 kWh
Total Units of electrical energy consumed = (y-x) Units
The rate of electricity is given in terms of per unit cost. If the cost of per Unit electrical energy is $R, then the total amount charged for the consumption of electrical energy is given by the multiplication of $R and number of Units consumed.
Therefore, the total electricity bill for one month
= $ (y-x)R
If you want to cross verify your electricity bill, you just need to take the kWh reading of your energy meter at the beginning and end of month. After that take difference of the two readings and multiply it by unit rate of electricity to get the actual amount of electricity bill.