Power Consumption Calculator: How To Calculate Electricity Use?

The power consumption calculator calculates how units of electricity (kilowatt-hours or kWh) a device draws per hour, per day, per week, and month.

How to compute electric consumption?

You only need to know the wattage of the unit, and how long you run it at that wattage.

In the 2 examples below, you will also find how to calculate the electrical bill (cost of running an electric-powered device) using the average price of electricity ($0.1319 per kWh).


Here is how many watts do common household electric-powered devices use.

Electricity Bill Calculation

Electric consumption depends on only one thing: the power of a device. On a specification sheet, you will find power or wattage (expressed in Watts).

The power consumption calculator above calculates how many kWh a certain device draws. For example, a 1,000 W device draws this many kWh if running for a certain period of time:

We can calculate how much impact this will have on our monthly electricity bill. For that, we need to know the price of electricity. Let’s presume that we run a 1,000 W air conditioner continuously for 1 month, with the average price of electricity being $0.1319 per kWh.

In the monthly bill, we will have to pay for 360 kWh of electricity. Here is how we can calculate the monthly electricity bill:

Electricity Cost = 360 kWh * $0.1319/kWh = $47.48

In short, running a 1,000 W unit continuously for a month will, on average, cost about $50.

Let’s look at the 2 examples where we will estimate electricity usage:

Example 1: Electricity Usage Of 500W Washing Machine Running For 3 Hours

How much electricity will average wash use? Let’s presume that we have a 500W washing machine that runs for 3 hours. Just plug the 500W in the power consumption calculator above, and we get:

calculation on electricity usage

We see that the 500W washing machine uses 0.5 kWh per hour. In 3 hours, that is 1.5 kWh. To get the dollar amount, we need to multiply electric consumption by the cost of electricity. If we presume $0.1319 per kWh electricity cost, one wash will cost us:

Electricity Cost = 1.5 kWh * $0.1319/kWh = $0.20

Example 2: Air Conditioner Power Consumption Per Month (3,000W AC Unit)

Summers can be hot. Let’s presume we install a 3,000W mini-split air conditioner (3,000W is equal to about 30,000 BTU). We will calculate how much will be running such a device cost per month if we have it turned on 24 hours per day. Realistically, we run an AC unit for about 8 per day, and we’ll calculate electricity expenditure for that as well.

Let’s use the electricity usage calculator above:

We see that every hour, a 3,000W device uses 3 kWh of electric energy. Running it for a whole month will burn 2,160 kWh of electricity. Let’s calculate the cost of that:

Electricity Cost = 2160 kWh * $0.1319/kWh = $284,90

As we can see, running it 24 hours per day will end up in a $284,90 increase in our monthly electricity bill. Realistically, however, we use it 8 hours per day, which will cost us less than $100 per month.

3 thoughts on “Power Consumption Calculator: How To Calculate Electricity Use?”

  1. Respected Sir
    When we use an electric heater with a rating of 1000 watts, how many units does it consume in eighteen hours?

    • Hi Bahadar, unit of electricity is usually a kilowatt-hour (kWh). 1000 watt electric heater consumes 1 kWh per hour. That 18 kWh in 18 hours, hope this helps.


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