How to calculate electricity

Calculate Electricity Consumption in 4 Easy Steps


Step 01

Watts Per Day

To calculate energy consumption costs, simply multiply the unit’s wattage by the number of hours you use it to find the number of watt-hours consumed each day. For example, let’s say you use a 125 watt television for three hours per day. By multiplying the wattage by the number of hours used per day, we find that you are using 375 watt-hours per day.

125 watts X 3 hours =
375 watt-hours per day


Step 02

Convert to Kilowatts

But electricity is measured in kilowatt hours on your electricity bill. Since we know that 1 kilowatt is equal to 1,000 watts, calculating how many kWh a particular device uses is as easy as dividing by 1,000.

375 watt-hours per day / 1000 =
0.375 kWh per day

Step 03

Usage Over a Month Period

Now to find out how much that’s actually going to cost you on your electric bill, you’ll have to take the equation a bit further. First you’ll need to figure out how many kWh the TV uses per month.

375 watt-hours per day X 30 days =
11.25 kWh per month

Step 04

Figuring Out the Cost

Next, pull out your last electric bill and see how much you pay per kWh. For this example, let’s say you pay 10 pence per kilowatt hour. To find how much the TV is costing you in a month, multiply your electricity rate by the kWh per month that you calculated above.

11.25 kWh per month X £0.10 per kWh =
£1.13 per month

Another Example

Here’s another more costly example: Your refrigerator runs 24 hours a day. Most refrigerators consume 300-780 watts of electricity. Let’s assume you bought a model that uses only 300 watts.

300 watts X 24 hours = 7,200 watt-hours per day

7,200 watt-hours per day / 1000 = 7.2 kWh per day

7.2 kWh per day X 30 days = 216 kWh per month

216 kWh per month x £0.10 per kWh = £21.60 per month


Common Wattages for Household Appliances

The wattage on appliances or electronics varies by device. Typically, older model appliances use more energy, but newer models tend to be more efficient. You can also purchase energy rating A appliances, which are among the most efficient appliances. 

Coffee maker 900-1200 watts
Microwave 750-1100 watts
Toaster 800-1400 watts
Dishwasher 1200-2400 watts
Washer 350-500 watts
Dryer 1800-5000 watts
Iron 100-1800 watts
Ceiling fan 65-175 watts
Space heater (40gal) 4500-5500 watts
Hair dryer 1200-1875 watts
Laptop 50 watts
Computer monitor 150 watts
Computer tower 120 watts
Television 19″-36″ 65-133 watts
Television 53″-61″ 170 watts



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