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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.

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How to misquote this site

and how to misinterpret the calculator results

Probably better than half of the people who quote figures from this site in newspaper articles and blogs make some kind of mistake either minor or major.  So readers are likely misinterpreting the results, too.  So here's a rundown of the most common mistakes, so you can make sure you're not going down the wrong path.  This page is really a primer on how to quote and use the site correctly, not how to misquote and misinterpret it, but the provocative title of this page gets more people to read it.  You're here, aren't you?  Anyway, let's get started.  But first, let me remind members of the media that I'm available for interviews and to check your articles for accuracy before you run them.  Take me up on it, it's free.

Electric rates vary widely!

You can't quote electrical costs without knowing the price of electricity, and everyone's rate is different.  I've found rates ranging from 12 to 50 per kWh from the same provider!  So writing, "Mr. Electricity says it costs 50 to dry a load of clothes in an electric dryer" is wrong, because that's not what I say.  More accurate is, "It costs about 50 to dry a load of clothes in an electric dryer, assuming a rate of 15 per kWh."

There's really no such thing as a "typical" or "normal" rate for electricity.  But I have to use something for the examples on this site, so I use 15, which is a reasonable example, but not necessarily "typical" or "normal", and certainly not average.  Let's see why average rates aren't a good choice for examples.

Most utility rates are tiered, meaning that excessive use is billed at a higher rate.  This is important because your savings are also figured at the highest rate you're paying.  For example, let's say you pay 9/kWh for the first 500 kWh, and then 15/kWh for use above that.  If you normally use 900 kWh a month, then every kWh you save reduces your bill by 15.  (Well, once you get your use below 500 kWh, then your savings will be 9 kWh, but you get the point.)  Some utilities have four or five tiers, with the rate getting ever higher the more you use.

To find your own savings, you should generally choose the highest rate you're currently paying, because that's the rate you'll start saving at.  Don't use the average rate.  To find your highest rate, just look at your bill.  For more information about how you're billed, see the page on the cost of electricity.

"It costs 50 to dry a load of clothes in an electric dryer." "An electric dryer often costs around 50 per load."
"It costs about 50 to dry a load of clothes in an electric dryer, assuming a rate of 15 per kWh."
Everyone's cost of electricity is different. Rates can vary from 12 to 50 per kWh from the same provider.
"...using the average rate of 15 per kWh..."
"...using a typical rate of 15 per kWh..."
"...assuming 15 per kWh..." (or)

"...using a rate of 15 per kWh..."
15 is not the average rate in the U.S. It's hard to say whether it's "typical", since we're not sure there really is a "typical" rate, but that's better than saying "average", which is clearly wrong.  The easy way out is to just not identify the rate as average or typical, just list the rate you're assuming.
"...using the average rate of 12 per kWh..."

"...assuming 15 per kWh..." (or)

"...using a rate of 15 per kWh..."
While 12 is the national average, the average is a poor choice for examples, since savings are realized at the highest tier someone is paying, which is usually more than the average.
"Electricity costs 14 per kWh in New York."

"The average price of electricity in New York was 14 per kWh in 2003."
Whenever I list a price for a state I clearly identify it as an average for the whole state.  As I keep saying, everyone's rate is different.

Device wattages are just examples!

Different models use different amounts of electricity.  Not every computer uses the same amount of juice, and not every TV does either.  I thought this would be obvious, but from the reader mail I get, apparently it's not.  So please don't think that the examples on this site are accurate for your particular computer, TV, or whatever.  You'll need to measure the wattage of your device to get accurate results for the model you actually own.

"Mr. Electricity says a 42" plasma TV uses 240 watts." "Mr. Electricity says a typical [or average] 42" plasma TV uses around 240 watts." Different models use different amounts of juice!  Also, my figures are usually the average for all models, which is a little different from "an average TV", but I know you have to say something, and this is close enough.

Some devices use less than their rated wattage

Some devices don't run at full power all the time.  For example, I list a water heater at 3800 watts, but the water heater doesn't run continuously.  It shuts off when the water gets hot enough.  Then there are devices that use energy according to how hard you run them a stereo uses more power the louder you set it, and less power the lower you set it.  Likewise, I list a microwave oven at 1440 watts, but that's only if it's running at the highest setting.  (Plus, the top setting on your microwave could be less than 1440 watts, as mentioned above.)  So realize that things like heaters and AC's don't actually run continuously, and things like stereos and microwave ovens don't always run at full power.  For most of the other items it's safe to use the listed wattage.  By the way, I solved the problem of refrigerators not running continuously by listing the average wattage for fridges in the calculator (and identifying it as such).

"An electric water heater uses 3800 watts. So in 24 hours it uses 24x3800= 91,200 watt-hours." "An electric water heater uses 3800 watts, but it doesn't run continuously. A typical family might pay around $40.48/mo. to run their heater."
Some devices, like water heaters, don't run continuously.  So you can't just multiply their rated wattage times the number of hours you're using them.
"A microwave oven uses 1440 watts. If you use a microwave for 10 minutes a day for 30 days, that's 7.2 kWh."
"A 1440-watt microwave used on the highest setting for 10 minutes a day for 30 days uses 7.2 kWh."
First, some ovens are more powerful than others, and therefore use more energy.  1440 watts is the upper end, some ovens use less.  And whatever the top setting is on the microwave, it can be run at a lower power level.  So, we need to identify the size of the oven (in watts), and If we're assuming that use is at the highest level, we need to say so.
"A typical dryer consumes about 5,000 watts." (eHow)
"An electric dryer costs about $0.43 a load at a sample rate of 15/kWh." (or...)

"An electric dryer uses about 3.3 kWh for a 45-minute load."
First, if we're talking about an electric dryer (vs. a gas dryer), we need to say so.  Next, as with most appliances, dryer wattage varies by model, from about 4000 to 6000 watts.  But most importantly, knowing the wattage isn't that helpful in the first place.  What the reader really wants to know is the cost per load (or the kWh per load, so they can calculate the cost using their own local rate for electricity).

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Be especially careful when figuring clothes washer or dryer costs

The clothes washer/dryer results were so frequently misunderstood that I removed them from the general-purpose calculator, and now the calculator gives the results an a per-load basis, which is more meaningful.  I also refer calculator users to the pages on the site which cover washer/dryer costs in detail.  Unfortunately people still sometimes misquote the laundry figures.  In some cases I have no idea how they came up with their results, or in other cases they're using the wrong table.  (One table shows the total cost of electric + water, one shows just the electric cost without water.)  Then there's the common case of not acknowledging the assumptions:  Your laundry cost will vary from my examples by quite a lot if your local fuel and water rates, water heater temperature, and groundwater temperature vary very much from my examples.  So if you're figuring your laundry costs, be extra careful, since this is an area where frequent mistakes are made for some reason.  So the previous section for an example.

There is no such thing as "watts per hour"

Electrical usage is measured in either watts (the rate at any instant), or watt-hours or kilowatt-hours (the amount used in an hour).  Thus, a 100-watt light bulb uses 100 watts, or 100 watt-hours in an hour.  It does not use "100 watts per hour", since there is no such animal.  That's like saying you weigh 150 pounds per hour.  Likewise, you don't pay for electricity by the kilowatt, you pay for it by the kilowatt-hour.  See more on how electricity is measured.

My figures are almost never "as much as"

I rarely tell you the maximum amount you could save.  That's not as helpful as telling you the typical, realistic savings, so that's what I do.  So when someone says, "Mr. Electricity says you can save as much as $150 a year from washing in cold instead of hot," that's wrong.  You could actually save much more than that, but $150 is realistic, using good figures for the assumptions.

My name is Michael Bluejay, not Michael BlueJay

The J isn't capitalized.  This is easy to get right, since my name is spelled correctly all over my site.  This was too much a challenge for Reuters to get right, though.  And whenever any reporter can't spell my name right, expect them to get something else wrong, too (like Reuters did).  While I'm at it, there's no "www" in my web address, either; almost everyone adds the www, even though it doesn't appear in the browser's address bar.

Examples of getting things wrong

WCPO Channel 9, May 2011
  • They quote an electric rate of 10 "a kilowatt".  First, electricity is charged by the kilowatt-hour, not the kilowatt, and second, 10 is too low as a sample rate, and is actually less than the national average.  I'm currently using 15/kWh on this site.
  • They say a coffeemaker running at 6 watts when idle costs $1.25/mo., assuming the 10 rate.  In fact it would cost only $0.44/mo.. (6 watts x 24 hrs/day x 30.5 days/month 1000 kw/w x 10).
  • "A few cell phone chargers now shut off when the phone is unplugged, though most don't."  Actually, it's the opposite.  Even my ancient 2004-era LG VI-5225 charger shuts off when the phone is unplugged.  Even if the charger doesn't shut off, the piddling 0.x watts it would use should be the least of your concerns, as I explain on the energy vampires page.

©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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