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.
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:
- Under the Start Menu go to your Control Panel.
- Under the Control Panel, click on Power Options.
- 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.
