In a report Wednesday, the environmental group Greenpeace looked at 19 online companies’ efforts to reduce their clouds’ reliance on “dirty energy.”

The group said only Apple was fueling its data centers with 100 percent renewable energy, but applauded Facebook, Google and three other online companies for having the same goal.

Based on Greenpeace’s Green Energy Index, Facebook came in at 49 percent; Google, 48 percent; and Microsoft Corp., which also has large data center operations in Iowa, at 29 percent.

The Washington, D.C., group looked at issues like energy transparency, renewable energy commitment and siting policies and energy efficiency.

Greenpeace, a longtime critic of the power that data centers consume, said the energy needed to power online searches, music downloads and other activities would rank among the top six if compared with countries.

Online energy demand is expected to grow by 60 percent or more over the next six years.

Iowa has become a data center hub to serve that growing demand for Internet access, in large part because of its renewable energy development.

“In the U.S., there are now nine states that are getting 10 percent or more of their electricity from wind power, with Iowa (25 percent) — a data center hub — topping the list,” the group said.

In Iowa, Google has invested $1.5 billion in data center operations in Council Bluffs. Facebook is building a $300 million data center in Altoona that’s expected to grow to $1 billion, and Microsoft has invested nearly $900 million in West Des Moines.

West Des Moines is expected to draw another large data center project, with an assessed taxable value of $255 million, city documents indicated last month.

The project would create 84 jobs. The company behind the project has not yet been revealed.

Greenpeace lauded Facebook’s decision last year in choosing Iowa over Nebraska for its fourth data center. The group said Facebook has helped drive additional investment in wind energy.

Facebook chose Iowa because it had a “more willing utility to help Facebook meet its renewable goals. Just two weeks after Facebook’s announcement, MidAmerican Energy, the local utility in Iowa, announced plans to invest $1.9 billion to increase its wind generation by 1,050 megawatts.”

“That plan simultaneously marked the largest investment in Iowa’s history and the world’s largest order of wind turbines,” Greenpeace said.

Facebook has since announced an agreement with Mid­American to purchase energy from a new wind project near its data center to allow it to fully power the facility with renewable energy.

In addition, Greenpeace said, “Facebook’s decision to spurn Nebraska has spurred debate in that state Legislature to strengthen policies to support renewable energy investment, so that Nebraska can be more competitive for future data center business.”

Greenpeace also pointed to Google’s decision to sign five long-term power purchase agreements for renewable energy, helping to green the grid for its data centers in Iowa, Oklahoma, and Finland.

“In addition to greening its data centers, Google has invested over $1 billion in 15 renewable energy projects,” Greenpeace said, including projects in Iowa and the world’s largest solar plant in Southern California.

The group also noted that Microsoft and Facebook weighed in on Iowa’s discussion over distributed power generation — such as solar energy, wind and other sources of energy that are developed close to where the power is consumed.