The U.S.-based electronics retailer Best Buy has begun selling renewable energy credits in the form of a $10 plastic card called “Green Your Phone.”

While the concept behind the card is to encourage customers who buy mobile phones to offset their phone’s energy consumption with green energy credits, the card is available to anyone who simply wants to boost their “green cred.” Each card goes toward promoting 500 kilowatt-hours of renewable energy, about as much energy that’s needed to manufacture and operate two mobile phones for two years.

Offered in partnership with Renewable Energy Choice of Boulder, Colorado, the Green Your Phone cards debut today at all 1,000 of Best Buy’s U.S. locations. Renewable Energy Choice also provided 10,000 cards for free to Best Buy Mobile employees as a way to kick-start the campaign.

Consumer electronics already account for a large portion of the U.S.’s energy consumption, and their impact is expected to grow. By 2010, such appliances are likely to account for 40 percent of the average individual’s energy use.

“Green Your Phone provides our customers with a tangible way to support renewable energy,” said Scott Moore, vice president of marketing for Best Buy Mobile.