The Walton family, owners of Walmart, donated millions of dollars to organizations opposed to government-backed incentives for solar power production, according to a report by the Institute for Local Self-Reliance (ILRS). And, says the report, the family, by way of a solar panel manufacturer that it controls, supported an Arizona regulation allowing the state's largest utility to impose a fee on households and businesses that install rooftop solar panels.

ILRS provided VICE News exclusive access to its report prior to its publication Thursday.

"We've been struggling with a Walmart economy for many years," Stacy Mitchell of ILRS told VICE News. "The middle class has shrunk and the number of working poor has increased. But one of the real highlights on the horizon is what's happening with rooftop solar, which allows consumers to have an ownership stake in energy production and it's creating a lot of well-paying jobs. That's a future we can't allow corporate interests and the Walton family to hold us back from."

Solar power production in the United States grew 36 percent in 2012, according to the latest report of the Interstate Renewable Energy Council. Rooftop solar installations account for much of that growth. According to the Solar Energy Industries Association, over 500,000 households and businesses in the United States generate electricity from rooftop solar arrays. Half of all home and business solar installations were installed in just the last two years.

The cost of buying and installing rooftop solar has plummeted and in many states customers can sell the excess power they produce to their utility company, delivering cost savings because they're buying less energy from utilities and generating revenue from the electricity they sell.

"Rooftop solar is something that many utilities have come to see as a threat to their future profits," Mitchell told VICE News.

It's a threat, she says, the industry is not taking lightly. She points to Arizona.

Last November, Arizona regulators granted the state's largest utility, Arizona Public Service, the authority to charge customers a fee for installing rooftop panels. The fee will run three to six dollars per month for customers depending on the size of their solar array.

The fee might seem small but it cuts into the long-term cost savings that have driven investment toward rooftop solar installations. The Solar Energy Industries Association estimates that customers save between $5 and $10 per month with rooftop solar arrays. The Arizona fee, says ILRS, helps maintain utility industry dominance over electricity production by halving the cost savings to customers.

One of the key factors in the APS victory, says Mitchell, was support for APS from a Walton family-controlled solar power company, First Solar. At the time, says Mitchell, APS was being cast as an enemy of renewable energy generation in a state that is ground zero for new solar energy generation. First Solar, she says, gave APS the appearance of having solar industry support.

'Until they are willing to look at the core aspects of how they do business, than their concern for the environment will continue to be nothing but a public image, rather then substance.'

The Walton family owns about a 30 percent stake in First Solar, according to documents filed with the US Securities and Exchange Commission.

First Solar did not respond to a VICE News request to comment on the reasons for its support of the Arizona fee or if it was currently involved in campaigns in other states to limit utility customer incentives for installing rooftop solar panels.

Spokesperson Stephen Krum referred VICE News to a June 2013 opinion piece in theArizona Republic, written by the company's CEO James Hughes.

"Studies show that the cost per installed watt of utility-scale systems is as little as one third that of rooftop systems," Hughes said.

In its 2013 annual report, however, the company identifies rooftop solar as a threat to its future profitability.

"We face numerous difficulties in executing our Long Term Strategic Plan," the report says, "including [… ]difficulty in competing against competitors who may gain in profitability and financial strength over time by successfully participating in the global rooftop […] solar market."

"This is not the Walton's saying there's no room for solar in their's or Walmart's future but only solar that's centrally-owned and benefits wealthy investors," says Mitchell. "It's an economic model that says the rest of us don't get to own anything and there's only a few descent, well-paying jobs. It's a model that has been very beneficial to the Walton family."

The solar industry now employs more people than the coal sector and installers earn an average of $24 per hour, according the Solar Foundation, which promotes the solar energy industry.

The Walton family's backing of anti-solar campaigns comes through its grant making as well. Between 2010 and 2013 the Walton Family Foundation (WFF) gave nearly $4.5 million in grants to organizations linked to repeals of state-level renewable energy incentives, including rooftop solar arrays, according to ILSR.

WFF granted roughly $800,000 to the American Enterprise Institute, $575,000 to Americans for Prosperity, and $150,000 to the Heritage Foundation, among others.

Walmart pledged in 2005 to source all of its energy from renewables. The company says over 24 percent of its electricity comes from clean energy technologies, an amount ILSR disputes, pointing to US Environmental Protection Agency data of three percent.

The company topped the 2014 Fortune 500 list of top revenue-generating companies. Christie, Jim, and Alice Walton were eighth, ninth, and tenth respectively on the 2014 Forbes list of wealthiest individuals in the world.

"The Walton family, if they really want to address the core environmental challenges that we face," Mitchell told VICE News, "they need to fundamentally reconsider how they operate."

She added: "Until they are willing to look at the core aspects of how they do business, than their concern for the environment will continue to be nothing but a public image, rather then substance. In particular they need to stop impeding rooftop solar."

WFF did not respond to a VICE News request for comment on its political contributions.

Walmart did not respond to a request to comment on progress toward meeting its renewable energy goal.