Each device that uses electricity to operate, such as the computer from which you read this text, consumes an amount of electricity.

To calculate this consumption just know the power of the device and the time of use of it, for example, if we want to know how much energy a 5500W shower connected for 15 minutes, your energy consumption will be:

But this calculation shows us that joule (J) is not an efficient unit in this case, since the above calculation only refers to a 15-minute shower, imagine the consumption of this shower in a house with 4 residents taking a shower of 15 minutes every day in the month.

For the spent energy to be understood in a more practical way we can define another unit of measure, which although not adopted in the SI, is more convenient.

This unit is the **kilowatt hour (kWh).**

To calculate the shower consumption of the previous example in this unit consider its power in kW and the time of use in hours, then we will have:

The most interesting thing about adopting this unit is that if we know the price charged per kWh, we can calculate how much money will be spent on this consumption.

For example:

Consider that in your city the power company has a tariff of 0.300710 R $ / kWh, so the consumption of the 5500W electric shower on for 15 minutes will be:

If we consider the case of a family of 4 who uses the shower daily for 15 minutes, the monthly cost of energy spent on it will be: