It's Earth Day on April 22, so what are you doing to help the environment? As well as recycling and using low energy lightbulbs and so on, one way to save a lot of energy is to use devices more efficiently. Even if you are one of the few people who don't believe in man-made climate change, saving energy means saving money, which no one can complain about! Computers use lots of energy - in offices, only lighting consumes more - but they are also full of energy saving potential. I've done some research into PC energy usage and myths, and come up with four easy ways to save energy on your PC.

Turn off your PC

This may seem obvious, but some people believe that you will shorten a PC's lifespan by turning it on and off. This is simply untrue, and as an OS will perform useful maintenance during shutdown, it will help a PC to run better as well as cutting energy use. If a computer is on for days without a proper shutdown, not only will lots of energy be used, but it will get slower. Some PC parts, such as hard drives, last longer if they are turned off when not in use. Computers also draw power when turned off - which will surprise many people. Unplugging a computer when not in use therefore also saves energy. This is all manual management, but there are also ways to save energy by altering power usage settings in your operating system.

Use power management

When a PC is on, there are likely to be times when it's not being used, and this is where power management comes in. A lot can be saved by putting the screen into low-power mode and by letting the computer go into sleep mode.

In Windows, power management is accessed by clicking the Power Options icon in the control panel, while on OSX it's the Energy Saver icon in System Preferences. With both you can choose from a selection of power profiles, or set up a custom profile. Set the monitor to power down after a few minutes of inactivity, as it only takes a second to wake up and uses much less energy that way (see below). Also, set the hard drive to sleep when possible (easier in OSX than Windows, unfortunately).

Computers - especially Windows PCs - take a little longer to wake up than screens, so you may prefer to allow more time before your PC goes to sleep. However, a lot of energy will be saved in sleep mode and as it only takes a few moments to wake up a system, it's not such a bad trade off. On average, desktops use 70W when active and just 9W in low power or sleep mode, which is a huge saving. While laptops already use much less energy than desktops, all of this advice is still valid and can amount to significant energy savings no matter which you use.

Don't use a screensaver

My apologies, but screensavers are an unfortunate and wasteful relic from the days of cathode-ray monitors. Back then, a still image on screen for hours would literally be burned into the screen. An animated screensaver was a sensible solution to that problem. With today's LCD monitors, however, there's no reason to have one. LCD monitors use less than a quarter of the energy required for their cathode ray counterparts, and even more is saved because they are able to switch on much faster.

Screensavers may look nice, but they are unnecessary for modern LCD monitors which can go into low power mode and wake up quickly. When sleeping, LCD monitors on average use 90% less electricity than when active - a huge saving that is lost by using screensavers, which keep monitors running on full power.

Watch multitasking

Keeping applications open unnecessarily makes processors work more, creating more heat and increasing the use of cooling systems, all of which use energy. Thoughtfully managing active applications helps efficiency, as computers will run faster and be less prone to crashing.

Checking the start-up list to see if there are apps that don't need to be running will help. Some programs, like Windows Live Messenger, like to open from start-up, but it's much better to just open an application when needed. When browsing, watch how many windows or tabs are open. Flash and video on a site can really make your computer work hard - so try not to keep lots of pages with that type of media open at the same time.

[References: http://www.dssw.co.uk/research/computer_energy_consumption.html http://en.wikipedia.org/wiki/PC_power_management]