WORCESTER — A wind power experiment has come to an end at Walmart.

The Arkansas-based operator of discount retail stores removed turbines from the parking lot of its Worcester supercenter in the last week and will now evaluate what it learned there and at two other U.S. sites, a spokeswoman for the company said.

"We're going through the data to figure out what we learned, and we're applying those lessons in a variety of renewable energy projects," said Kara Greco, Walmart director of sustainability communications.

Twelve small turbines were installed on the top of 48-foot parking-lot lights when Wal-Mart Stores Inc. opened its 209,000-square-foot supercenter in May 2010. At the time, it was only the second Walmart site in the country with turbines installed in a parking lot.

The turbines were financed and installed by a private company to generate power to be sold to Walmart over a period of years for the parking lot lights and the store. Shoppers could usually count on seeing them spinning in the breeze.

Yet in the last five years, the market for small wind-generating installations has changed, and Walmart's renewable energy agenda has evolved.

Reduced subsidies from state governments have impacted demand in the U.S. market for small and medium-size wind turbines, according to the clean energy research firm Navigant Research. At the same time, solar energy systems have become more affordable.

Nearly 3,700 new small wind turbines were purchased in 2012 in the United States, about half as many as in 2011, the U.S. Department of Energy reported. Small turbine sales totaled $101 million in 2012, down about 12 percent from the year before.

The company that financed, designed and installed the Worcester turbines also no longer exists. Deerpath Energy of Marblehead was sold in 2010 to Southwest Windpower, an Arizona business. In 2013, Oregon turbine maker XZERES Corp. bought the assets of Southwest.

For Walmart, wind power is the dominant renewable energy it uses in Mexico, according to Ms. Greco. U.S. company Foundation Windpower also installed and still operates a large turbine at a Walmart distribution center in Tehama, California.

But solar power has become the dominant renewable energy the company uses in the United States. Walmart expects to unveil 400 solar installations over the next four years in the United States. "In the U.S., solar is definitely our largest portion of renewable energy," Ms. Greco said. "It really depends on what's the most economic."

Contact Lisa Eckelbecker at lisa.eckelbecker@telegram.com.