Opponents of a city of Portland tax measure on the November ballot today released a study showing that Measure 26-201, the Portland Clean Energy Initiative, could raise $43 million to $79 million annually in taxes.

That's a bigger number than a preliminary estimate from the city's Revenue Division, which said in June 2017 that the measure was likely to raise $35 million to $51 million. (Proponents of the measure tweaked it slightly after the city produced its estimate.)

Opponents of the tax, who include many of the big retailers that would probably pay it—such as Walmart, Comcast and Fred Meyer—hired Portland consulting firm ECONorthwest to analyze the measure. The company produced its report in July but it was only released today.

The tax measure, which has the support of 150 community organizations and City Commissioner Chloe Eudaly, would levy a 1 percent surcharge on the revenues of large retailers that have more than $500,000 in retail sales in Portland and more than $1 billion in retail sales nationally.

The money would be used to fund energy efficiency and carbon reduction projects for low-income Portlanders and communities of color and to provide job training in the energy field for those groups.

ECONorthwest wrote that ambiguities in key definitions of what exactly constitutes "retail sales" and which companies qualify as "large retailers."

"The large estimated range is primarily a function of ambiguous wording in the Initiative itself and uncertainty over how the Initiative would be implemented by the City of Portland if it were to be passed," the report says.

Proponents aren't buying it.

"The Portland Clean Energy Initiative is well-written and broadly supported by all segments of our city," said Dr. Adriana Voss-Andreae, the executive director of 350PDX and one of the measure's chief petitioners. "Our initiative will create huge energy savings and job opportunities for low-income Portlanders. The few wealthy corporations that will be subject to the surcharge would rather spend thousands on a biased study than pay their fair share so that low-income Portlanders can have clean energy and living-wage jobs."