With a deadline looming, Texas regulators are struggling to make up their minds about the finer points of the Ray L. Hunt family’s $18 billion proposal to buy and reshape Oncor, the state’s biggest electric utility.

The biggest remaining sticking point is this question: Should the Dallas-based oil family allow Oncor, under a new corporate structure, to collect hundreds of millions of ratepayer dollars — normally earmarked for federal taxes — that the company wouldn't actually have to pay? 

On Thursday, Public Utility Commissioner Brandy Marty Marquez said she was uncomfortable with the idea.

“There’s something very lucrative and attractive about this particular structure, and I cannot be okay with a windfall on the back of those ratepayers,” she said at an open meeting of the three-member commission that must decide whether the deal fits the public interest. “In my opinion, they’re not entitled to any of it.”

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But, Marty Marquez added, she would be open to a plan for shareholders and ratepayers to share that wealth — if the deal “heavily favored” the ratepayer.

Her two colleagues were less committal.

Chairman Donna Nelson said that she did not consider the arrangement a “windfall” for investors, but said she would consider such a sharing plan. She also suggested that eliminating other risks in the deal might make allowing investors to pocket the tax savings more palatable. 

Commissioner Ken Anderson said he’s “still mulling that over” but called sharing a “real benefit that could compensate for the risk” involved in other parts of the deal.

The commission has been mulling for months, but its time is running short. Commissioners must decide on the deal by sometime in March.

The stakes are even higher than ownership of Oncor, whose 119,000 miles of transmission and distribution lines deliver power to more than three million homes and businesses in North and West Texas. Hunt's plan is the lynchpin of efforts by Oncor’s parent, Energy Future Holdings, to emerge from one of the largest bankruptcies in American history.

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To save on taxes, Hunt wants to divide Oncor into a real estate investment trust.

That financial structure has long served the real estate world. Shopping malls, for instance, commonly use it, as investors back a broad entity that rents space and other assets to individual stores.

But such trusts have never been tried at a large utility, and critics call it risky.

The idea would divide a utility into two companies. One would own the assets (power lines, trucks and transformers, for instance), while the other, much smaller “operating” company would rent the equipment. In Oncor’s case, the “asset” company would hold about 97 percent of the income — largely untaxed.

Federal law requires these trusts to pay out at least 90 percent of their income to shareholders thorough dividends.

The idea has drawn fierce pushback from a host of groups, including consumer advocates, big industrial power users, staff experts at the utility commission and Oncor officials.

One of critics’ biggest complaints: Hunt calls for the new Oncor to keep charging ratepayers what it normally collects in federal taxes — even though the company would no longer send that money to Washington. 

Proponents say those tax savings make for a healthy company that can borrow money cheaply as it makes costly improvements to the electric grid.

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In December, written testimony from Darryl Tietjen, who oversees rate regulation for the commission, characterized the Hunt plan as a “substantial transfer of wealth from ratepayers to shareholders” totaling nearly $250 million each year.

Approving that shift, he added, would likely spur Oncor’s peers to follow because of the “very obvious tax benefits that would accrue to shareholders."

Since then, another giant utility, Houston-based CenterPoint, said it is exploring the structure.

The commissioners have been clearer on a few issues: They like the Hunts, and they would love to see an end to Energy Future’s bankruptcy, which has stretched nearly two years and eaten up plenty of the agency’s time.

“I think there is real benefit to the Hunts owning Oncor," Anderson said. “I think they’d be great owners. I like the idea of local folks owning it who have to eat their own cooking.”

Hunt says the trust status is a deal breaker, but they are open to hashing out other concerns with the deal.

“We understand completely the desire for transparency and certainly protections,” Hunter L. Hunt, CEO of Hunt Consolidated, told the commissioners Thursday. “We have an ironclad commitment to meet the obligations of y’all.”