How to Find the Cost of Electricity

wireWhen I dry my clothes on the line instead of the dryer it saves electricity, but how much exactly? I asked Doug and he told me all about currents and voltage, but really when it comes down to it, I just want to know how much money I’m saving.  Here’s how to find out exactly how much the electricity costs to run your appliances. 

The key is to look at the label on your appliance or power cord.  Find the number for the Amps.  It might be a number with the letter “A” next to it.  (If there is one for Input and another one for Output, use the number for Input.) On the label for my laptop, the number I want is 1.5, because it is the one next to the A.

You’ll also need a recent electric bill. Look in the fine print on the bill and find the average price per kWh. On my bill it says, “The average price you paid for electric service this month was 15 cents per kWh.”

Now to find the cost of electricity for my laptop:

1. Start with the number next to the letter A or Amps on the label. 1.5
2. In the US, multiply by 120 for appliances that you plug into the wall (except use 240 for dryers).
Outside of the US, find your voltage here.
x 120
3. Divide by 1000. / 1000
4. Multiply by the number of hours (I’ll use one hour to keep it simple). x 1
5. Multiply by the average kWh price on your electric bill. x 0.15
This is the cost to run your appliance for that amount of time: = .027

It costs almost three cents an hour to charge my laptop.  At first I thought, big deal?  Until I realized it is 65 cents a day, and $236.52 a year!  If I remember to unplug it overnight for 12 hours, that will save $118.26 a year.


Let’s do another example.  I wanted to know how much my dryer costs to run. My dryer is ancient, but it keeps on working. It is definitely not a new high-efficiency model. On this label, the number to use is 23 Amps. Doug checked this with his amp meter, and it’s right.

1. Start with the number next to the letter A or Amps on the label. 23
2. In the US, multiply by 120 for appliances that you plug into the wall (except use 240 for dryers).
Outside of the US, find your voltage here.
x 240 (for dryers)
3. Divide by 1000. / 1000
4. Multiply by the number of hours (It takes 45 minutes to dry a load, so I’ll use .75). x 0.75
5. Multiply by the average kWh price on your electric bill. x 0.15
This is the cost to run your appliance for that amount of time: = .621

This is how I know that every time I dry a load of clothes on the line instead of using the dryer, it saves 62 cents.  For my family that’s about $10 a month.


Here’s a shortcut for light bulbs.  Let’s see how much it costs to burn an incandescent 100 watt bulb.

1. Start with the number of watts for the light bulb. 100
2. Divide by 1000. / 1000
3. Multiply by the number of hours (I’ll use one hour to keep it simple). x 1
4. Multiply by the average kWh price on your electric bill. x 0.15
This is the cost to burn the light bulb for that amount of time: = .015

It costs 1.5 cents to burn a 100 watt incandescent light bulb for an hour. Not a lot, but something that adds up over time. Keeping it on for 8 hours a day costs $43.80 a year. It’s easy to see how replacing it with a compact flourescent bulb can make a difference. The CFL bulb only uses 26 watts instead of 100, so it saves $32.41 a year.

Once I learned how to do this, I went around my apartment and figured out the cost of electricity for the things I use the most.  Since then, our electric bills have been noticeably lower than the year before.  Knowing about this really helped me to focus my efforts for using less electricity.

About Rachel

I write about practical tips that will help you simplify at home. Connect with me on Pinterest and Twitter.


  1. Kirstin says:

    You are incredible. This is an awesome blog! Thanks for sharing your smarts!!!

  2. thanks for the information. I have been unsure on whether or not to turn the lap top off at night.

    Now, i will for sure!

  3. wilsonclan says:

    very interesting. thx!

  4. Christi~berrymomma says:

    Cool. Of all the so called “important” things we are taught in school, why didn’t I ever come away with things like this that are actually valuable, useable information?

    Thanks! I’m teaching my kiddos this tomorrow.

  5. smallnotebook says:

    I’m so glad this is helpful. Be sure to actually unplug the cables for electronics that use remotes, have a power light, or a clock. Laptops left plugged in will still drain power, so unplug those when you aren’t using them. We use a power strip with a switch to turn off the TV and DVD so they won’t continue to draw power.

    For all of you homeschooling moms, here are the “proper” engineering terms:
    First we found the Amps.
    Then we multiplied it by the Voltage.
    Amps x Voltage = Watts.
    Then we divided by 1000 to convert to Kilowatts.
    Kilowatts x Time = Kilowatt-hours (kWh)

    • Just so you know, your website is wonderful :)

      I was wondering: do you actually turn off your computer, leave it unplugged, or take the plug out of the wall? I can’t believe how much that would save in a year!

      PS: I also hang my clothes and the nice thing about it is it doesn’t damage them as much as the dryer does and you use less energy so mother nature is happy!

  6. thanks for this post! so practical and so easy to understand.

    so i’ve been kicking around the idea of line-drying. our dryer is about 7 years old — so i’m guessing it’s fairly energy efficient. but it seems so silly to be generating all this hot air when it’s already 90 degrees outside.

    how long does it take you to hang up a load of laundry? do you do smaller daily loads or larger loads a few times a week?

  7. smallnotebook says:

    For line drying, it’s pretty fun. I usually do 4 loads a week, one a day on Monday to Thursday. It’s usually enough clothes to fill a large-capacity washer. I try to get the clothes washed by lunchtime, and then hang them up to dry. It takes 5 or 10 minutes to hang them on the line. I don’t use any clothespins, I just drape them over the line. Clothespins might be better, now that I’m thinking about it. When the afternoon’s over and they’re mostly dry, I take them down and put them in the dryer for about 5 minutes to let them tumble and finish drying. Sometimes I leave them out overnight and just gather them the next morning. I do have a small indoor drying rack for clothes I don’t want to display outside.

    It is extra effort, but the thing is, I really like it. It’s domesticity in a nice way, because while I’m hanging the clothes, Lane is playing outside with me. The best part is how it feels to see a row of little baby clothes hanging on the line. If it were just a chore, I’m not sure the effort would be worth the money savings. But since it’s a nice way to be outside, and the clothes dry naturally for free, I’ll keep doing it. I’m actually disappointed when it rains and I have to use the dryer.

  8. This is awesome! Thanks for the info. I’m printing it out…

  9. Wow! What incredibly cool information! My hubby and I were just talking yesterday that we needed to hang our clothes out as much as possible to see if we could save a little on the electric bill. Now I’ll tell him exactly how much we’re saving!

    And double thanks for the homeschooling “education-ese.”

  10. Mrs. Gunning says:

    I am so glad Mrs. Brigham referenced to you here! I love what I am seeing so far, and this post is excellent. :)
    With the cost of everything rising (I’m wondering when we’ll be taxed to breathe… ;) ), becoming wise to the actual cost of things is a great idea for anyone/everyone! Thank you for sharing this, I did not know how to actually calculate the cost!

  11. Oh good grief! I had the same reaction to the laptop charge cost of .03 cents, but when you add it up (and all other charging items like it), it’s downright terrifying. Thanks for the reality check!

  12. Your laptop charging is not at a constant rate shown (that will be “peak”). It will draw that at the beginning when the batteries are empty and then lessen as the battery fills up until there is just a little trickle. If you are using a laptop or a desktop computer look for the “sleep” modes and set them like 5 or 10 minutes instead of the 30-60 minute defaults (may need to reference your owners manual).

    Get a Kill-a-Watt meter (online for $25) to see.

    Generally your biggest energy hogs are easy to spot… A/C, Furnace, Hot Water Heater, Refrigerator, Television, Dryer, Freezers, Stove/Microwave,light bulbs, and then all the small electronics with remote power-on features or those power “cubes” (not in that order, depending on your use patterns). Tackle fixing the top 90% of your energy use first (or the easy things around).

    Example with A/C: leave it off in the morning and open windows to get cool air from outside, when it starts to get hot then close the windows and only turn the circulation fan on (that will draw cooler basement air up and balance the house out),use overhead fans and box fans near work areas. Later only turn the A/C on when it gets hot again. And set the A/C so it’s not icy like a supermarket. Then watch the temperature outside in the evening and turn off the A/C when you can open the windows again to bring in cool air. Or finish off your basement and work there (with that portable laptop!). If no one is home all day, get a programmable thermostat to leave the A/C off except 20 minutes before you’re about to get home and do the evening window opening trick.


  13. Thanks for the advice J, I definitely think that starting at the top with the biggest energy-using appliances is the way to go. My friend reduced her electric bill by half when she turned down the temperature on her electric hot water heater.

  14. do you know how long i have wondered exactly how much it costs in electricity to run our well? (actually, specifically if the expensive electricity it uses costs more than the rather low price of the city water saved by watering and filling pools with the well instead)

    and do you know how many people ive asked who havent had a clue how to go about comparing the two?

  15. Wow, I calculated how much we could save by switching from 100 watt incandescent bulbs to the 26 watt “green” equivalents.

    It’s about $250 per year for 8 bulbs. Those new bulbs last about 100 times longer too. Payback period is less than 2 months.

  16. Heating the house is number one the most expensive, followed by water then clothes drying, real hard to cut back much on those, I dont think gadgets or lightbulbs are so bad, esp when its easy to change the lightbulbs, but otherwise, im gonna have to guess good insulation, and making use of what is free, outside clothes drying, wearing sweaters in winter is as much as you can practically do

  17. I have recessed lights in my house. When you turn it on all of them burn at once like 4 in a room. It has taken out electricity bills to $100 or more.

    I dont know how to reduce these costs. Changing the bulbs in the recessed lights and so many of them is also expensive.

  18. Dan, perhaps you could start by changing the light bulbs that get used the most, since they would have the biggest impact on your electricity bill. We replaced ours gradually instead of doing them all at once.

  19. Schemilix says:

    We’re learning this in school, but uh, why do we divide by 1000 sorry? Only bit I don’t get. >>’ I mean, the coulombs and stuff, I get that you multiply the amps by the voltage to get the charge, and that the energy used is the charge times the time frame, wouldn’t you just time the energy by the price per kilowatt hour?

  20. Schemilix says:

    Nevermind, you want it in kilowatts, so you divide it by a thousand.

  21. This is an excellent article! It is great real life application of math! I will share this with my colleagues!

  22. Yay! Just got Stumbled to my favorite website. :D

  23. I have heard over the years that keeping a freezer full makes it not have to work as much, and therefore cutting down on the cost. Also if the freezer is stored outside or in a garage where it is warmer in the summer it would take more to keep it cold. So how does play into this equation?

  24. Jamie, that’s right, if the freezer is full of frozen food or ice, then it doesn’t have to work as hard. It does take more amps to cool the air if the freezer is in a warm garage, but I don’t know how much without measuring with an amp meter.

    • Kimberly says:

      I am looking in to getting a deep freezer to put into our garage, and we are worried that living in Arizona where it gets very hot in our garage, it will take too much energy to run it. I have been looking around at different deep freezers and they all say how much kilowatts per year they use, do you know how to convert that to find out how much energy it uses?

  25. WOW!! I just found your site today and I must say that it is really great and informative.
    I did not realize how much I was spending in electricity until I saw this post and I went around and looked at the different items I have plugged in. Many things are going to get unplugged when they are not in use. Thanks for sharing.

  26. Except that the “innards” of those “green” CFL’s are full of highly toxic materials from what I understand, especially if you happen to drop and break one in your house while changing it out. I read you might as well bring the HazMat team to clean up the mess of chemicals it will leave in the carpet and air. I read this in an email newsletter I get about healthier living from WC Douglass. Look it up on Wikipedia here-

  27. This is great! We got our electricity bill late last week and I could not believe it was $213! There are only 3 of us in our little house. I started running around the house unplugging things and turning off lights. This will really come in handy tonight when I explain to my husband that leaving the fan on all day when we are not home is not such a great idea. Thanks for the info!

    Amanda’s last blog post..Free Ticket to Disney!