What is a kiloWatt-hour a.k.a kWh? (part 1)



We have a new and improved page on "What is kWh?"

This is one of the most important articles for people just starting out understanding their electricity bill!  While I am proud of my famous What's a Watt blog, this one is just as important.

The bill you get from your power company gives you your electricity consumption in kilowatt-hours (kWh).  The price you pay for that electricity is in cents per kWh.  In Georgia, I pay around 9 cents/kWh, up North they pay round 17 cents/kWh, and in Hawaii they pay almost 30 cents/kWh! Thanks Nebraska for this handy chart.

To get your final bill amount, you simply multiply your usage (total kWh/month) times the amount you pay per kWh (your rate).  Unfortunately, you also have to pay some flat rate fees your utility charges.  Pretty simple right?

This is very obvious, but your goal is to reduce the kWh you consume each month!  So how do you achieve this?  The best targets are the big power (remember power = watt) users that are on for the longest amount of time (energy (kWh) = power (watt) * time).

When I was working at a Nuclear power plant (no, I don't glow) I remember being confused by Watts and kilo-Watt hours (I was an intern ok!) and I remember reading Michael Bluejay's great write up on the Watt/kWh .  Here is another good article from Appropedia.

I am going to go into much more detail in part 2 of What is a kWh.  I dont want to turn too many readers away at the technical stuff by writing too much at once.  It is important, so PLEASE don't blow it off.  Ignorance is not bliss when it comes to saving money and helping the environment.

Use the kilowatt hour calculator below to see how much it costs you to run an appliance.  Look at the cord or on the appliance to see how many watts the appliance uses and fill in how long you keep the appliance on per day.   If minutes, divide by 60 to get the units in hours. You'll have to know how much your utility charges you per kwh.  If you don't know your rate, you can find the average rate in your state by looking at the first image on the  Electricity Graphics page.

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Learn more about the kilo-Watt-hour in part 2!

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I find this fascinating. I just installed solar for my entire home & pool. I need to understand how all this works...I get so many questions!
I wrote the IRS last year and they wrote back that "Per Publication 502 you can include in medical expenses amounts you pay for oxygen and oxygen equipment to relieve breathing problems caused by a medical condition." It then goes into detail of how you must prove the electric use. If you would like more detail you can write to They were very quick in answering my question and sent almost 2 pages of information about it and other sources and phone #'s where you can ask questions. It's not enough to retire on but every little bit adds up! Again thanks for your help. Jim
I'm not sure how you come up with 240 kW but when I take 280 X 24 X 30 and then divide by 1000 I come up with 202. However, when you mulitply that by .065 that gives me the $13.10. I want to thank you because of this I can deduct a part of my yearly electric charge off my federal and state taxes. You've been a great help. Jim
ckmapawatt's picture
Sorry, the 240 should have been 280. How are you able to deduct it from your taxes?
I'm on an oxygen converter 24/7. It says it uses 280 watts. I pay .065 p/kWh. Will it cost $42.00 a month? Thanks
ckmapawatt's picture
If it uses 280 watts all the time.. .240 kW * 24 hours/day * 30 days/month * .065 $/kWh = $13.10
ckmapawatt's picture
Wow, I never knew that, but it makes sense!
Am trying to find out something about electricity that is being metered, but not consumed in my home. I'm told that this might be called either arcing electricity or dumping electricity. Maybe it's got another name. Am in disagreement with Arizona power company. Was told that one month in 2011 that my electricity usage was 102% higher than the average of 100 homes of similar size within 0.12 miles away from me. Have you ever heard of this?
ckmapawatt's picture
I havent heard of this. What about a <a href="" rel="nofollow">TED 5000</a>? I haven't heard of dumping electricity though? How many kWh did you use and what month was it? Where did you get the data on the other homes?
Ok, I might be going a little bit on a limb here but hear me out. I'm thinking about going off the grid completely, the whole 72 car batteries in the basement and going solar. I have alot of high energy use equipment in my house, air conditioners, all appliances, and about 10 different computers and a few servers thrown in too... if I just measure up all the wattage of all the devices and multiply buy the hours used I'll come out with X. Now how do I figure up how many solar panels and how many batteries I need to become fully sustainable? Alot of the mumble jumble on the solar panel is kinda hurting my brain.


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