Save and Go Green: Computer Energy Saving

A few months ago, after discussing ways to save energy with some people at work, a co-worker said that he unplugs his computer at night to save on energy. I had never thought of just simply unplugging your computer to save additional energy. This is probably a pretty common question most people would like to know, but don’t really know the true answer to. I wasn’t totally sure myself so I looked into how much energy do our computers use and ways to save money on cutting their energy usage.

Saving Computer Energy
Photo by functoruser.

Computer Energy Use

I never realized that computer use as much energy as they do, especially desktop computers. PCs alone can consume anywhere from 50 – 250 watts of energy!!! The monitor itself also consumes tons of energy, with a traditional CRT monitor consuming more than newer LCD monitors. Laptops on the other hand use far less energy at around 45 watts and are way more energy efficient than your average desktop computer. In order to get a better idea of how much it would cost to run your computer, I crunched some numbers and determined how much it would cost to run.

I first want to preface the numbers I calculated with some basic definitions and assumptions I made. I found a great definition on Wikipedia that sums up how a kilowatt-hour is calculated:

If a 100 watt light bulb is turned on for one hour, the energy used is 100 watt-hours or 0.1 kilowatt-hour

Most energy companies charge customers on a kilowatt-hour basis, making it an important number in my calculations. There are several assumptions I will be making throughout the rest of this article used for my calculations:

  • The computer is in use for 2 hours a day for 7 days a week.
  • Each value displayed is in kilowatt-hours, unless specified with a dollar sign.
  • The cost of electricity is $0.12 per kilowatt-hour.

24/7 Computer Energy Usage

Watts Used Day Week Month Year Year Cost
Desktop Computer 120 2.88 20.22 87.6 1051.2 $126.14
Laptop 45 1.13 7.9 34.22 410.63 $49.28
Old CRT Monitor 80 1.92 13.48 58.4 700.8 $84.10
LCD Monitor 35 0.84 5.9 25.55 306.6 $36.79

As you can see from the above table, a desktop computer with a LCD monitor running 24/7 can cost you over $160 per year. That’s a huge number considering most desktop computers can cost as little as double that amount. This not only has a major affect on your wallet, but also has a huge impact on the environment. There is no need to waste that much energy when the average person only uses their home computer a few hours a day.

Let’s see how much you can save by simply setting the sleep or standby functionality on your computer.

Energy Saving: Sleeping Computer

Watts Used Day Week Month Year Year Cost Year Savings
Sleeping Computer 6 0.37 2.61 11.32 135.78 $16.29 $109.85
Sleeping Laptop 1 0.11 0.79 3.41 40.88 $4.91 $44.37
Sleeping CRT Monitor 5 0.27 1.9 8.21 98.55 $11.83 $72.27
Sleeping LCD Monitor 3 0.14 0.95 4.14 49.64 $5.96 $30.84

By simply turning the sleep functionality on your computer and monitor, that $160 above goes down to only $20 per year.

Setting the sleep functionality on your computer is a great idea, but should only be used if you forget to turn off your computer. The best way to really save money on computer energy use is to turn off and unplug your computer when not in use. Even if you turn your computer off or allow it to sleep, it still is using a slight amount of energy. Though the energy difference is small, it can really add up if you allow your computer to sleep instead of turning it off.

Energy Saving: Turning Off/Unplugging Computer

Watts Used Day Week Month Year Year Cost Year Savings
Turned Off Computer 3 0.31 2.15 9.31 111.69 $13.40 $112.74
Unplugged Computer 0 0.24 1.68 7.3 87.6 $10.51 $115.63
Unplugged Laptop 0 0.09 0.63 2.74 32.85 $3.94 $45.33
Unplugged CRT Monitor 0 0.16 1.12 4.87 58.4 $7.01 $77.09
Unplugged LCD Monitor 0 0.07 0.49 2.13 25.55 $3.07 $33.73

You can save even more money by unplugging your computer whenever you are not using it. Not just that, you will be using less than 1/10th of the amount of energy that you would be using if you keep your computer running at all times.

Save Energy on Computer Accessories

You can save additional energy on top of what you can save on your computer. Think about all the accessories you can have for you computer. Most people have common accessories like printers, modems, routers, speakers and many others. The table below shows the cost to run various computer accessories.

24/7 Computer Accessory Energy Usage

Watts Used Day Week Month Year Year Cost
Home Inkjet Printer 50 0.15 1.02 4.44 53.29 $6.39
Home Multi-function Printer 30 0.32 2.23 9.64 115.71 $13.89
Cable Modem 9 0.22 1.52 6.57 78.84 $9.46
Router 5 0.12 0.84 3.65 43.8 $5.26

The printer is one of the larger energy users of of all computer accessories. All-in-one printers in particular use much more energy than traditional printers because they have much more functionality. Many accessories including your router and modem are not able to go into standby and therefore are running at all times. Even though they use far less energy that a computer, it still makes a difference to turn them off or unplug them when you are not using them.

Energy Saving: Computer Accessories

Day Week Month Year Year Cost Year Savings
Home Inkjet Printer 0.05 0.35 1.52 18.25 $2.19 $4.20
Home Multi-function Printer 0.08 0.54 2.34 28.11 $3.37 $10.51
Cable Modem 0.02 0.13 0.55 6.57 $0.79 $3.77
Router 0.01 0.07 0.3 3.65 $0.44 $9.02

Easy Ways to Save

One very easy way to save money is to ensure that you set the sleep functionality on your computer. This can be easily done on a Windows machine by:

  1. Under the Start Menu go to your Control Panel.
  2. Under the Control Panel, click on Power Options.
  3. Click on the Power Schemes tab to be able to set all of your power settings.

Under the tab I described above, you can set the amount of time your computer is inactive before it will go into standby ( or sleep ). You monitor can also automatically be turned off through this menu as well. Sorry to Mac and Linux users, but it should be pretty simple to find out how to set these settings on your machine.

One extremely easy way to make sure you computer and its accessories are all turned off is to use a power cord. I have my computer, monitor and any accessories plugged into one power cord. When I am completely finished using my computer, I simply switch off the entire strip. It’s really that simple and it makes it extremely easy to ensure that computer and its accessories are using absolutely no power.

If you are in need have to use a computer all the time, you could try using a laptop instead of a traditional desktop and monitor combination. Not only does the laptop use 1/3 of the energy, but they are much more portable and takes up less room. It can be hard to use a laptop all the time, so you could also look into buying a more energy efficient computer. Many of these computers use the same amount of energy as a laptop, but are as powerful as a traditional desktop computer.

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  1. Very good and informative article. Going to bookmark this one for later reference when I do my next power evaluation.

    The Green Routines last blog post..How to Make Money Recycling Aluminum Cans

  2. Really informative post and great charts for reference, thank you!

    Organically Tvs last blog post..A humorous and eye opening short film about plastic bags

  3. I’m very surprised that there is a difference between “turned off” and “unplugged”.

  4. I recently came accross your blog and have been reading along. I thought I would leave my first comment. I dont know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.


  5. Good and very informative post.

    Living off grid we are very energy aware. We turn everything off when not in use, it’s amazing how much leaving things on standby can still use a lot off power.

  6. You rock. World needs more souls like you.

  7. Hmmm. I have always gone by the energy star sticker, perhaps there is more to it.

  8. Going green with your IT is something everyone should do (or at least try to do). There are a lot more resources available these days.

  9. We have to go green in every aspect of our lives. This means that we have to pay attention with everything at home, in the office, and everywhere which can influence our environment. For those who always use computer have to care about the energy needed for working with it.

  10. That’s why I switched from desktop to laptop, much better on energy for me.

  11. I’ve always wondered how much the sleep function actually saves. I only use my laptop now so I use a lot less power than I used to.

    • Rosario
    • September 1st, 2009

    Sounds very interesting.. great post, thanks

  12. You can also save a heap of energy by reducing the screen resolution. Im not sure of the hard numbers but I know its significant because my laptops battery lasts twice as long when its set up this way. You’ll also do your eyes a massive favor.

  13. I’m happy to see how much less power a laptop uses. Is it better to charge it up, unplug it and let it run down and then recharge, or have it sitting on charge all the time?

  14. Thank you, I recently purchased an energy saving desktop, and wondered what the cost to use a computer was in the first place. We started shutting down our computer at night & sleep it during the day now. I believe we will save money, and this post proves it! Being a 3 computer household, this really adds up.

  15. I have been following your advice and I do see a difference on my monthly electricity bill.

  16. Sounds very interesting, it’s amazing how much leaving things on standby can still use a lot off power.

  17. this year we started our campaign in the office to unplug electronic devices when unused. we had 7% decrease in our electrical bill…
    not bad for just unplugging. :)

    thanks for sharing.

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