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Calculate your electric cost

Device / Wattage (wH/hr)

Amount used per day

Cost of Electricity (per kWh)

Days used per month

 
Kilowatt Hours used: kWh/mo.
Cost per month: $
Cost per year: $

Don't misinterpret these results!
(1) Your particular computer, TV, etc. could use more or less energy than the samples listed here.
(2) Some things use more or less energy based on how high you crank them (e.g. ovens, stereos).
(3) You should generally choose highest electricity rate you're paying. See the Right and Wrong Way to Use the Calculator.


Google picks the ads, not me. I don't endorse the advertisers.


How much electricity do household items use?

Last update: June 2013

The calculator at right will give you a rough idea of how much electricity something uses and how much it costs you.  But there are some important caveats:

  1. Electricity rates vary widelyI've found rates from 12 to 50 per kWh from the same provider.  If you want results that are anywhere close to accurate, you'll need to check your own electric bill and find your actual kWh rate.  Your bill might have multiple kWh rates (e.g., one for "delivery" and one for "fuel"), and in that case you should to add up them all up to get the total kWh rate.  Most rates are tiered, meaning the higher your use, the higher the rate.  You should generally enter your highest tier into the calculator, because any energy you save will save you money at that highest tiered rate.

  2. Electrical use varies from model to model.  I thought this would be obvious, but in hundreds of blogs and forums people say things like, "Mr. Electricity says a computer uses 150 watts," which is a mischaracterization.  The calculator and table figures are just examples.  (See how to misquote this website.)

  3. Some devices use varying amounts of electricity.  An easy example is an oven, whose energy use depends on how high you crank it.  Perhaps a less obvious example is a washing machine, which effectively uses phenomenally more energy if you wash in hot rather than cold.  Then there's the refrigerator, which alternates between periods of full energy use while the compressor is running, and then next to nothing when the compressor shuts off.  (To solve this problem for fridges, the calculator lists the average wattage over time, not the higher amount used when the compressor runs.)

  4. Most devices don't run 24/7.  Therefore the "Hours per Day" and "Days per Month" fields in the calculator are crucial.  Even so, you might not have a good idea about how various appliances run.  So below we'll discuss which items use the most energy in a typical home.  You can also measure a device's usage yourself, which gives you the best information for your own situation.

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    Heating

    26,500 watts

    Elec. furnace, 2000sf, cold climate

    7941 watts

    Elec. furnace, 1000sf, warm climate

    1440 watts

    Electric space heater (high)

    900 watts

    Electric space heater (medium)

    600 watts

    Electric space heater (low)

    750 watts

    Gas furnace (for the blower)

    1100 watts

    Waterbed heater

    450 watts

    Waterbed heater (avg. 10 hrs./day)

    Cooling

    3500 watts

    Central Air Conditioner (2.5 tons)

    1440 watts

    Window unit AC, huge

    900 watts

    Window unit AC, medium

    500 watts

    Tiny-ass window unit AC

    325-425 watts

    Fan only for central AC (no cooling)

    More efficient cooling

    400 watts

    Evaporative cooler

    350 watts

    Whole-house fan

    100 watts

    Floor or box fan (high speed)

    90 watts

    52" ceiling fan (high speed)

    75 watts

    48" ceiling fan (high speed)

    55 watts

    36" ceiling fan (high speed)

    24 watts

    42" ceiling fan (low speed)

    Major appliances

    4400 watts

    Clothes dryer (electric)

    see sep. page

    Washing machine

    3800 watts

    Water heater (electric)

    200-700 watts

    Refrigerator (compressor)

    57-160 watts

    Refrigerator (average)

    3600 watts

    Dishwasher (washer heats water)

    2000 watts

    Electric oven, 350F

    1178 watts

    Electric oven, self-cleaning mode
    (takes 4.5 hrs, 5.3 kWh total)

    1200 watts

    Dishwasher (dry cycle)

    200 watts
    Dishwasher (no water heating or drying)

    Lighting

    60 watts

    60-watt light bulb (incandescent)

    18 watts

    CFL light bulb (60-watt equivalent)

    5

    Night light

    0.5

    LED night light

    Computers  (see more about electrical use of computers)

    150-340 watts

    Desktop Computer & 17" CRT monitor

    1-20 watts

    Desktop Computer & Monitor (in sleep mode)

    90 watts

    17" CRT monitor

    40 watts

    17" LCD monitor

    45 watts

    Laptop computer

    Televisions & Videogames

    191-474 watts

    50-56" Plasma television

    210-322 watts

    50-56" LCD television

    150-206 watts

    50-56" DLP television

    188-464 watts

    42" Plasma television

    91-236 watts

    42" LCD television

    98-156 watts

    32" LCD television

    55-90 watts

    19" CRT television

    45 watts

    HD cable box (varies by model)

    194 watts

    PS3

    185 watts

    Xbox 360

    70 watts

    Xbox

    30 watts

    PS2

    18 watts

    Nintendo Wii (source)

    Other

    1440 watts

    Microwave oven or 4-slot Toaster

    900 watts

    Coffee maker

    800 watts

    Range burner

    4 watts

    Clock radio

    3 watt-hours

    Total energy stored by an alkaline AA battery. This is to put batteries into perspective. If you could power your clock radio with a AA battery, it wouldn't even last an hour. We have more on batteries on our Guide to Household Batteries.

    Wattage varies from model to model!  Figures above are examples.  See How to Misquote this Website.

    Data for specific models of appliances is available at the Power Consumption Database.
    Some devices use a little energy even when they're not on.  This is called standby power, or vampire power.  In most cases it's negligible, the main exception being cable TV boxes.  My standby power page has more info on this.

U.S. household energy

U.S. household energy use by appliance

Electrical usage of household items

The chart at right shows how the average home used energy (not just electricity) in 2007. (Dept. of Energy)  Of course, heating is a bigger chunk in the winter and air conditioning is a bigger chunk in the summer. For example, AC accounts for 60-70% of the average home's summertime power bill in Austin. (Austin Energy)  Places which aren't as hot in summer don't get a break, because they're generally colder in winter and so more is spent on heating.  Below at right is the energy use for an all-electric home in Tallahassee, Florida, which shows that 60% of the energy goes to heating and cooling. (City of Tallahassee)

At the bottom of this page is a chart showing the relative use of various appliances. (DoE)  Note that this doesn't really jibe with the pie chart above from the DoE.  (Refrigerators and appliances use different amounts in the different charts.)  If I can ever find the time, I'll try to make my own chart.

Here are some other websites that give sample costs for various household items considering how much those items are used:

Individual Appliances

At far right is a table listing examples of the wattage of common household appliances.

Appliances that create or remove heat use the most electricity.  In the table at right, appliances that make things hot are listed in red and ones that make things cold are listed in blue. As you can see, together they dwarf everything else on the list.

Don't like my table? Here's another table from Generator Sales.  A database which lists power data for specific models of products is Power Consumption Database.

Remember that electrical usage varies from model to model, and that the tables on this site are just examples. (See how to misinterpret this website.)


Figuring the use of your own items

The best way to know how much energy your stuff uses is to measure it.  You can do that easily with a cheap watt-hour meter, or you can do it for free by timing your electric meter.  I explain all this on the page about measuring your electrical use.

A shortcut, though a little less accurate, is to just look at the product's label.  Nearly everything you can plug into the wall has a label that says how much electricity it uses. (It may be printed directly into the plastic or metal.)  You may have to hunt for the label.  It's often located on the bottom or side of the device, or possibly where the power cord enters the unit.  If the device is powered with an AC/DC adapter, the electrical rating is usually listed on the adapter itself.

If the label gives only the number of amps and not the number of watts, then just multiply the amps by 120 to get the number of watts. (Amps x Volts = Watts, and most U.S. electricity is ~120 volts. So a hot plate rated at 6 amps uses 6 x 120 = 720 watts, on the highest setting.  Most other countries use 240 volts instead of 120, so outside of North America and Japan use 240 instead of 120 in your calculations.)  Note that if a device is powered by a transformer (one of those great big plugs), then the transformer has converted the electricity from AC to DC, so you need to multiply by the DC voltage, not the AC voltage of 120. For example, if the device says "INPUT 9V, 0.5A", then that's 9 volts x 0.5 amps = 4.5 watts.

You may have noticed that appliances may be labeled 110, 115, or 120 volts.  U.S. appliances are actually designed to accept a range of voltages, between 110-120 volts, and the exact voltage coming out of your electrical socket can vary depending on conditions at the power plant and in your own home.  Let's just agree that when we say 120 volts, we understand that it's actually a range from 110-120.  And just use 120 for your calculations (unless you're outside of North America or Japan, in which case you probably have 220-240 volts).

Your device might actually list a huge voltage range, like 100-240V. That just means that it will work with any country's voltage. For your calculations, use the voltage for the country where you're plugging the device in.

Some important caveats:

  1. The amount of electricity listed on the label is the maximum amount that the appliance will ever use. For example, a 300-watt refrigerator will only run at 300 watts when the compressor's running (which is when it makes that humming sound, indicating that it's actually chilling the air inside). Most of the time the fridge just sits there, using only 5 watts or so for its electronics. If the amount of work done by a device varies up and down, then so does its energy use. (e.g., a stereo that can be turned up or down, an oven that can be set at various temperatures, a fridge that sometimes runs and sometimes doesn't, a computer that sometimes spins its various drives and sometimes has to use more of its brainpower, etc.) The label on computers is particularly useless; a computer labeled at 300 watts probably uses only about 100. (More on computers' electrical use.) In just a bit we'll cover how to measure the actual amount of electricity being used by a device

  2. Many consumer items are advertised according to their power output, not input. That means the stereo that says 30 watts on the box might actually require 50 watts to make 30 watts of sound (assuming the volume was cranked), and your 900-watt microwave oven might actually use 1400 watts (on its highest setting). That's because all electrical devices are inefficient -- they have to use some extra energy to do what they do.

  3. Some devices use energy even when they're not on. (Standby power)

Exercise: Pretend there's an energy crisis and they start rationing electricity.  You're given a bonus of 1000 watt-hours of electricity to use because you won a special drawing.  If you're choosing between using your stereo or your central air conditioner, how long could you run each? Assume that your stereo uses 30 watts and your AC uses 3500 watts. (see answer)

Exercise: The power adapter on your laptop computer says its output is 24V and 1.875 amps. The input specs aren't listed for some reason. What's the maximum number of watts your computer could ever use? (see answer)


Energy-saving strategies

Here's how much various strategies can save you.


Easy Strategies

Strategy

Up front cost Savings per year

(1) Use space heaters to heat only the rooms you're in (rather than a central system that heats the whole house), and turning off the heat when you're not home.

$80 $1023
(2) Use ceiling fans instead of the air conditioner $100
if you don't already have ceiling fans
$438
(3) Turn off lights you're not using $0 $274
(4) Use a clothesline or a laundry rack instead of a dryer $20 $196
(5) Sleep your computer when you're not using it $0 $178
(6) Wash laundry in cold water instead of hot or warm none $152
(7) Turn off a single 100-watt light bulb, from running constantly $0 $131
(8) Replace ten 60-watt light bulbs with compact fluorescents $32 $123
Total $232
once
$2515
every year
Aggressive Strategies
(9) Replace top-loading washer with front-loading washer $500 $99
(10) Replace 1992 fridge with a new Energy Star model $440
$75
Total $940
once
$174
every year

Assumptions:  (Calculations are always only as good as the assumptions.  See how to misquote this website.)
Sample electrical rate of 15/kWh.
(1) One 5000-watt central system, always on, running 40mins/hr. for four months, vs. two 1500-watt heaters running 8 hours a day for four months.  Of course, not everyone cant heat their living area adequately this way, but some can.
(2) A 2.5-ton, 3500-watt AC 24 hours a day (15 mins/hr) for five months, vs. two 48" ceiling fans on high (75 watts each), 12 hours/day.
(3) Five 100-watt light bulbs on for 10 hours a day when they don't need to be.
(4) 50/load as per the clothes dryers page, 7.5 loads a week.
(5) Computer on for 24 hrs/day @ 160 watts, vs. sleeping 21 hrs/day @ 5 watts
(6) Electric water heater; 7.5 loads/week.
(8) CFL's are 15 watts, lights run 5.5 hours a day.
(9) 1/3 hot washes, 2/3 warm washes, water heated electrically, electric dryer, 7.5 loads/week. Includes water costs.
(10) Replacing a 900 kWh/year fridge with a 400 kWh/year Energy Star model.  Non-Energy Star fridge costs $400 and saves $60/yr. All fridge sizes are 18cf.  Fridge prices checked at Sears in Nov. 2010.

 



Now see how to measure electrical use

Links checked: June 2013
©1998-2018 Michael Bluejay, Inc. All Rights Reserved. Unauthorized reprinting is prohibited.
All advice is given in good faith. We're not responsible for any errors or omissions. Electricity can kill you; if you're not competent to work on your electrical wiring then hire a professional to do it.
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