If you use 500w of power for one day u have used

Your device is 500W. If you plug your appliance with AC mains it will consume 500W. The device needs 500W of power to run smoothly. Now 1 unit of electricity is 1000W or 1kW. If an appliance of 1kW is running for 1 hour it will consume 1 unit of energy. Now your appliance is of 500W i.e. 500/1000=0.5kW(you have to convert in kilo watt). Now units consumed by your appliance will be: kilowatt rating*no. of hours

in 1 hour= 0.5*1 =0.5 units of electricity.

If it is running for 2 hours then= 0.5*2=1 unit of electricity

If it is running for 3 hours then= 0.5*3=1.5 unit of electricity

Depending on your Tariff you will get the bill, for eg.(just random value): Your electric utility company is charging units for Rs. 2, then your bill will be units consumed*cost of unit: in this case

for 1 hr: 0.5*2 = Rs. 1

for 2 hr: 1*2 = Rs. 2

for 3 hr: 1.5*2 = Rs. 3

Hope this helps.

Explanation: