Estimating Electricity Usage

When you get your electricity bill each month, you may not think a whole lot about what goes into it. But in reality, every appliance or electronic device adds a little something to your bill. By figuring out what the biggest energy hogs are in your home, you can adjust your usage by unplugging or simply using the device less. Every change you make should help whittle down your energy expenses.

Calculating the energy cost of an appliance or electronic device is fairly easy. Most devices have a label that lists how many watts it uses, either on the device or in the owner's manual. You will need to find this number to figure out how much the appliance is costing you. You will also need to estimate how many hours a day you use a particular appliance.

house hold appliances

The Wattage Label

wattage label

If you can't find the wattage label, there are other options to determine how much power your device uses. For example, you can purchase a wattage measuring device, such as the Kill A Watt®. Simply plug your appliance or electronic device into the Kill A Watt® to determine how much power it uses. Or you can contact the manufacturer, with your model number, to find out how many watts a particular device consumes. You can also check the list at the bottom of the page for common wattage on household devices. Though your particular device may vary, it should give you a rough estimate of the energy expenses related to the device.

Calculate Electricity Consumption - 4 Easy Steps


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

Convert to Kilowatts

But electricity is measure 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

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

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 cents 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

looking in the fridge

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 STAR appliances, which are among the most efficient appliances. According to the EPA, here's a list of typical wattage levels for your everyday devices.

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
household appliance