We're so dependent on our computers these days that most of us would be lost without them. They make communication, work and entertainment much easier — yet their negative effects on the environment are often overlooked.

The energy used in producing and operating personal and workplace computers is huge. Corporate IT equipment alone uses more than 22 billion kilowatt-hours per year, according to the U.S. Energy Information Administration, a branch of the Department of Energy.

But it's not only computers' energy consumption that's noteworthy; the manufacturing process and the materials involved are also important factors.

• Click here for FOXNews.com's Personal Technology Center.

About 4.6 million tons of computers and consumer-electronics waste are dumped in landfills each year in the U.S., according to Greenpeace, and fewer than 12 percent of discarded computers are recycled.

Aware of this problem, PC manufacturers are trying to go "green" by minimizing the use of toxic components such as lead and mercury and making the machines more energy-efficient.

But how can you know how green your computer really is?

Green Computers, or 'Greenwashed' Ones?

If you're looking for a new computer and are unsure about which models are eco-friendly, a good place to start is the Electronic Product Environmental Assessment Tool (EPEAT), devised by the Green Electronics Council based in Portland, Ore.

Devised for both companies and individual users, EPEAT's online database evaluates desktop computers, monitors and laptops based on their environmental features. Its criteria include:

— Reduction of use of hazardous substances such as cadmium, lead, mercury and flame retardants;

— Elimination of non-recyclable paints and coatings;

— Minimum of 65 percent recyclable or reusable parts;

— Upgradability with common tools;

— Energy Star-approved power-management system;

— Rechargeable battery recycling;

— Elimination of toxins in packing material;

— Recyclable packing materials.

Toshiba currently holds EPEAT's highest rating of 22 out of a possible 27 with the Portege R500-PPR50U notebook. Dozens of other laptops from Apple, ASUSTek, Dell, HP, Lenovo, Sony and Toshiba again tie for second place with ratings of 21 out of 27.

The top four desktops are variations of Lenovo's ThinkCenter M58, all scoring 20 out of 24. (The different base numbers indicate on how many criteria the manufacturer submitted the unit for consideration.)

Last on the list are four desktops from MPC and Positivo, all scoring zero out of 24.

According to the Green Electronics Council's first annual report, entitled "The Environmental Benefits of the Purchase or Sale of EPEAT Registered Products in 2006," increased sales of EPEAT-approved computer equipment have saved 13.7 billion kWh of electricity.

That's enough to power 1.2 million U.S. homes for a year.

Energy Efficiency

An average desktop system constantly uses between 90 and 280 watts, plus between 35 and 90 for the monitor. A typical laptop's energy consumption will be around 80 watts.

But participants in the Energy Star program, which was begun by the Environmental Protection Agency (EPA) in 1992, can be counted on to be more efficient.

Energy Star specifications were updated in mid-2007 for all types of computers, monitors and game consoles to include standby and sleep modes.

Qualifying computers are at least 80 percent more efficient than those without the label.

Keeping computers out of landfills

An estimated 50 million computers become obsolete annually, and appropriate disposal is becoming more of a problem.

If a computer is less than 5 years old, it can probably be put to good use by someone else and as such can be donated to a charity or refurbisher.

But if it's not working, the best option is to recycle it.

Computer manufacturers Acer, Apple, Gateway, HP and Dell will recycle your unwanted computers for free, provided they are their own brand.

For first-time Dell purchasers, the company will also recycle the old computer for free even if it's another brand.

Aside from that option, the best bet is to go to an FDA-authorized IT recycler. Their specialty is to help organizations and individuals avoid state and EPA penalties for improper electronics disposal — and they'll also guarantee that your hard-drive data will be erased.

ERevival LLC, based in Lyndhurst, N.J., is one of the East Coast's leading electronics and computer recycling companies, and claims that only 1 percent of the electronics it receives eRevival ends up as waste.

"If the item cannot be fixed, it is disassembled for any reusable parts. The reusable parts are remarketed or donated. The non-usable parts are sent to smelters and refiners," says eRevival owner Ketul Thaker.

Data Dumping

No matter what you decide to do with your unwanted PC, it's best to completely wipe all the data on the hard drive. Deleting a file simply removes it from the directory, but it remains on the drive. Even reformatting a drive can leave data intact and recoverable.

As aleady noted, FDA-authorized recycling companies have reliable methods for sanitizing hard drives. The two main procedures involve either complete data deletion using Department of Defense software — or hard-drive destruction.

Sonia Schenker of Back Thru The Future, an Ogdensburg, N.J., recycler specializing in data destruction, recommends that all storage media be removed from PCs, cameras and cell phones and handled separately from other recycling processes.

"This practice of segregating storage devices offers a more secure method of disposal and satisfies legal requirements for having auditable records of records disposal," Schenker says.

As the notion of "green" computing catches on, the EPA estimate that hazardous waste by will be reduced by 4 million pounds, and enough energy saved to power 2 million homes. That's bound to please any environmentally-minded technophile.