By Melissa Santos

The News Tribune

An initiative on the November ballot would create a new tax on carbon emissions in Washington state, with the goal of helping reduce pollution that contributes to global warming.

Initiative 732 would impose a tax of $15 per metric ton of carbon dioxide starting in July 2017, and increase the tax to $25 per metric ton starting in July 2018.

Supporters of the initiative say it would result in a 25-cent increase in gasoline prices, which would be offset by increased low-income family tax rebates, lower business taxes and a reduction in the state sales tax.

But opponents of I-732 said the plan also would increase household electricity costs by 20 percent — a number the initiative’s supporters dispute.

The claims: During this election season, the No on 732 campaign, which is sponsored by the Association of Washington Business, has claimed the initiative would significantly increase energy costs for families.

“Initiative 732 will put even more strains on household budgets,” read a statement on the No on 732 website. “It increases the price of electricity by 20 percent and natural gas by 15 percent, making it harder on Washington families already struggling to keep up with living expenses.”

Meanwhile, the Yes on I-732 campaign says the increase in electricity costs would be only about 5.3 percent.

They say the No on I-732 campaign based its 20 percent estimate on an incorrect calculation by the state Department of Commerce, which the department has since corrected.

The facts: A study commissioned by the No on I-732 campaign relied on a tax calculator from the state Department of Commerce that contained an error.

The error resulted in the department’s tax calculator overestimating how much I-732 would increase household electricity costs by about a factor of four, said Greg Nothstein, an energy policy specialist with the agency.

The Department of Commerce corrected the calculation error in its tax modeling tool last month, Nothstein said.

After learning of the error on Sept. 30, the No on 732 campaign asked its research firm to update its economic analysis using the corrected information from the Department of Commerce, a spokesman for the campaign said.

The updated study, which the No campaign sent to The News Tribune and The Olympian on Monday, now estimates that I-732 would cause household electricity costs to rise by about 5.4 percent by 2020 — roughly what the proponents of the initiative are estimating.

The No on 732 campaign is updating its website and other informational materials to reflect the new numbers, the campaign spokesman said Monday.

Conclusion: False. The claim that household electricity costs would go up 20 percent was based on faulty calculations. The actual increase would be about one-fourth of that.