HP recently pledged to double its purchase of renewable power from under 4 percent in 2008 to 8 percent by 2012. The company has also committed to reducing energy consumption and the resulting GHG emissions from HP-owned and HP-leased facilities worldwide to 16 percent below 2005 levels in two years.

HP is already participating in Austin’s Green Choice program, to purchase almost 20 million kilowatt hours of wind energy from wind farms in western Texas for two of its Austin data centers, which represents nearly 20 percent of the annual energy used by the two centers.

Dell was quick to respond to HP’s announcement by writing in its blog that it’s a “good first step for HP.” Dell pointed out that it “currently sources about 20 percent of its global energy use from green energy provided by utilities” and that it met its carbon-neutral goal more than five months ahead of schedule.

Dell went on to write:

We encourage HP to take today’s announcement a step further and commit to being carbon neutral. This would drive new efficiencies throughout its business, further engage employees and lead to a much higher level of green-energy investment worldwide (100 percent, according to the company’s 2007 definition).

Dell’s response is in line with other PR challenges it has made to competitors on sustainability issues.

But it’s not as if HP has been twiddling its thumbs when it comes to the environment. The company recently completed a 1.1-megawatt solar-electric power system on the roof of its printing technology research and development facility in San Diego.

In September, HP announced it has collected emissions data associated with its largest suppliers, which represents more than 80 percent of the company’s costs for materials, manufacturing and assembly of its products worldwide.

In April, HP became the first company to receive approval from the U.S. EPA to have the agency’s SmartWay logo displayed on a selection of its consumer product packaging.

Here’s a link to EPA’s list of Fortune 500 green-energy purchasing figures, Both HP and Dell are in the top 25.

HP recently topped the latest Vendor Matrix released by ABI Research.