Here is an list of energy efficiency tips related to computer usage.
Be Energy Smart
Set the Power Options on your computer to switch to sleep mode when it's not active. You can find the power options settings in your PC's Control Panel. When you're going to be away from your PC for more than a few minutes, set it to stand-by mode and turn off the monitor. You'd be surprised at the amount of energy saved by this simple act.
Go Flat
In addition to being mercury-free and recyclable, light-emitting diode (LED) displays deliver significant energy savings compared to cold cathode fluorescent lamp (CCFL) technology. Dell’s 15-inch LED displays, for example, consume an average of 43 percent less power at maximum brightness, resulting in extraordinary cost and carbon savings. LED displays are also thinner and lighter. Every flat panel monitor we sell meets the EPA's strict Energy Star 4.0 guidelines. And skip the screen savers. They contribute to energy waste by preventing a monitor from entering stand-by mode.
Print Wisely
Print only what you need and use recycled content paper whenever possible. Most printers today have a two-sided printing option which can dramatically reduce your paper consumption. Be sure to recycle used ink and toner cartridges. Dell includes a prepaid envelope in every ink and toner cartridge sold. Simply drop it in any mailbox and we'll take care of the rest.
Reuse and Recycle
Dell offers an array of convenient options to recycle or donate your used technology. We've also joined Goodwill to form the Reconnect program in several US cities, making recycling your PC as easy as a trip to local Goodwills. From free recycling on all Dell consumer products to donation programs that benefit the people in your own community, we make it easy to be green.
Offset the Rest
Once you've reduced your energy use where you can, support carbon offset projects such as reforestation that counter CO2 emissions. Dell has partnered with The Conservation Fund and Carbonfund.org Foundation, two nonprofit organizations dedicated to reducing carbon emissions and the effects of climate change, to launch the Plant a Tree for Me program.
Power supplies matter
Many of us use an older desktop PC for a file server. Older systems (5 to 7 years) tend to have low-efficiency power supplies, known to consume more energy than high-efficiency ones. You can upgrade to a high-efficiency (80 to 90 percent) power supply, as they are relatively inexpensive and widely available. (Power supplies are the silver boxes found on the back of most desktop PCs.)
Check the battery
If you have an older laptop and haven’t replaced the battery in a few years, you are most likely wasting energy. Laptop batteries wear out over time. As they get older, it takes the same energy to achieve consecutively shorter battery operating time and performance. Save some energy by recycling a worn-out battery and getting a new one.
"IV" 85 percent efficiency
Many computers as well as things like printers, external hard drives, scanners and speakers have external adapters (the cord that attaches to the wall). Newer adapters are marked with the International Energy Efficiency stamp of "IV" 85 percent efficiency; the new Energy Star external power suppliers are marked "V", at 87 percent efficiency. If you want to do your part and help save energy, you shouldn’t buy a new system with anything less.
A comprehensive article on greening your gadgets can be found here.