Data centers, the key backbone of the cloud, are growing larger and more energy intensive, prompting the Department of Energy (DOE) to launch a new initiative on Tuesday aimed at improving their energy efficiency.

According to DOE statistics, data center electricity use doubled between 2001 to 2006, from 30 to 60 billion kilowatt-hours of electricity, and stood at about 100 billion kilowatt-hours of electricity as of 2013. This amounts to about 2% of all U.S. electricity use and climbing.

Already, there are about 3 million data centers in the U.S., amounting to about one center per 100 people in the U.S., and this is expected to continue to grow as more computing applications for large and small companies are moved to these facilities.

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The new initiative aims to improve the energy efficiency of data centers across the U.S. by bringing them into the preexisting "Better Buildings Challenge", which the Obama administration established in 2011. The challenge is part of the Obama administration's efforts to improve the energy efficiency of the U.S. economy, thereby cutting emissions of greenhouse gases that warm the climate.

The launch on Tuesday includes 19 new partners, from ecommerce giant eBay and retailers like Home Depot and Staples to eight DOE labs, including the Los Alamos National Laboratory in New Mexico, where nuclear weapons research is conducted. The inclusion of large federal facilities is noteworthy, since 10% of the federal government's energy use is from data centers, according to DOE information.

The initiative also includes the EPA, part of the Justice Department, Michigan State University, National Renewable Energy Laboratory and the Social Security Administration. Two large realty companies with large data centers are also partnering with the DOE on this initiative, including CoreSite Realty Corporation and Digital Realty.

The data centers that are part of the new program together consume more than 90 megawatts of electricity per year, according to a press release. This would be enough to power 90,000 homes for a year.

According to the DOE, operators of "the vast majority" of data centers across the U.S. do not currently practice "energy management" to improve their efficiency and reduce energy costs.

Kathleen Hogan, DOE's deputy assistant secretary for energy efficiency, told Mashable in an interview that half of the energy used to power a data center is used for the cooling and powering of equipment, with the other half going to actually running the servers and other IT equipment.

Because most companies are turning over their data center IT technologies every three to five years, bringing in equipment that tends to be more efficient, Hogan says the focus of the initiative is on making gains in the efficiency of heating and cooling operations at these facilities.

“We’re all in a world where things are changing quickly and we see there is always new IT equipment out there all the time,” she said. “There’s a great opportunity to reduce the air conditioning loads in a data center," Hogan said.

The new initiative seeks to make all data centers operated by the partner companies and agencies at least 20% more efficient by 2020, Hogan added.

If all U.S. data centers met this efficiency goal, she said, it could yield about $2 billion in cost savings and save more than 20 billion kilowatt-hours of electricity by 2020.

According to Hogan, the new focus on data centers aims to “challenge as many data center managers, operators as possible.” She said a main component of the initiative calls for companies to share best practices with others, thereby creating a "solution network" that can accelerate the spread of more efficient technologies.

Companies with small data center footprints can also join the challenge by making efficiency improvements at just one data center, on the order of a 25% increase in energy efficiency within five years, Hogan said.

She said the sheer amount of data centers, from small ones located at office buildings to large ones that are large structures of their own, are now "pervasive" around the U.S. "even if we don’t see them.”